[v2,2/2] vfs: Add new setgid_create_acl test

Commit Message

Yang Xu (Fujitsu) July 26, 2022, 9:31 a.m. UTC

The current_umask() is stripped from the mode directly in the vfs if the
filesystem either doesn't support acls or the filesystem has been
mounted without posic acl support.

If the filesystem does support acls then current_umask() stripping is
deferred to posix_acl_create(). So when the filesystem calls
posix_acl_create() and there are no acls set or not supported then
current_umask() will be stripped.

If the parent directory has a default acl then permissions are based off
of that and current_umask() is ignored. Specifically, if the ACL has an
ACL_MASK entry, the group permissions correspond to the permissions of
the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
group permissions correspond to the permissions of the ACL_GROUP_OBJ
entry.

Here we only use setfacl to set default acl or add ACL_MASK to check
whether inode strip  S_ISGID works correctly.

Like umask test, this patch is also designed to test kernel patchset behaviour
"move S_ISGID stripping into the vfs* helper"

Signed-off-by: Yang Xu <[e-mail]>
---
1.add kernel commit id
2.move umask into parent process intead of child process
3.remove duplicated comment for ACL_GROUP_OBJ and ACL_MASK because
we have mentioned it before the function
 src/vfs/idmapped-mounts.c | 704 ++++++++++++++++++++++++++++++++++++++
 src/vfs/idmapped-mounts.h |   1 +
 src/vfs/vfstest.c         | 345 ++++++++++++++++++-
 tests/generic/999         |  33 ++
 tests/generic/999.out     |   2 +
 5 files changed, 1084 insertions(+), 1 deletion(-)
 create mode 100755 tests/generic/999
 create mode 100644 tests/generic/999.out

Comments

Christian Brauner Aug. 29, 2022, 1:20 p.m. UTC | #1

On Tue, Jul 26, 2022 at 05:31:21PM +0800, Yang Xu wrote:
> The current_umask() is stripped from the mode directly in the vfs if the
> filesystem either doesn't support acls or the filesystem has been
> mounted without posic acl support.
> 
> If the filesystem does support acls then current_umask() stripping is
> deferred to posix_acl_create(). So when the filesystem calls
> posix_acl_create() and there are no acls set or not supported then
> current_umask() will be stripped.
> 
> If the parent directory has a default acl then permissions are based off
> of that and current_umask() is ignored. Specifically, if the ACL has an
> ACL_MASK entry, the group permissions correspond to the permissions of
> the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
> group permissions correspond to the permissions of the ACL_GROUP_OBJ
> entry.
> 
> Here we only use setfacl to set default acl or add ACL_MASK to check
> whether inode strip  S_ISGID works correctly.
> 
> Like umask test, this patch is also designed to test kernel patchset behaviour
> "move S_ISGID stripping into the vfs* helper"
> 
> Signed-off-by: Yang Xu <[e-mail]>
> ---

Hey Yang,

Thanks for your patches! Just a minor comment below.

> 1.add kernel commit id
> 2.move umask into parent process intead of child process
> 3.remove duplicated comment for ACL_GROUP_OBJ and ACL_MASK because
> we have mentioned it before the function
>  src/vfs/idmapped-mounts.c | 704 ++++++++++++++++++++++++++++++++++++++
>  src/vfs/idmapped-mounts.h |   1 +
>  src/vfs/vfstest.c         | 345 ++++++++++++++++++-
>  tests/generic/999         |  33 ++
>  tests/generic/999.out     |   2 +
>  5 files changed, 1084 insertions(+), 1 deletion(-)
>  create mode 100755 tests/generic/999
>  create mode 100644 tests/generic/999.out
> 
> diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
> index f63ac44b..f934cf4a 100644
> --- a/src/vfs/idmapped-mounts.c
> +++ b/src/vfs/idmapped-mounts.c
> @@ -8083,6 +8083,700 @@ out:
>  	return fret;
>  }
>  
> +static int setgid_create_acl_idmapped(const struct vfstest_info *info)
> +{
> +	int fret = -1;
> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
> +	struct mount_attr attr = {
> +		.attr_set = MOUNT_ATTR_IDMAP,
> +	};
> +	pid_t pid;
> +	int tmpfile_fd = -EBADF;
> +	bool supported = false;
> +	char path[PATH_MAX];
> +	mode_t mode;
> +
> +	if (!caps_supported())
> +		return 0;
> +
> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
> +			      S_IWUSR |
> +			      S_IRGRP |
> +			      S_IWGRP |
> +			      S_IROTH |
> +			      S_IWOTH |
> +			      S_IXUSR |
> +			      S_IXGRP |
> +			      S_IXOTH |
> +			      S_ISGID), 0) {
> +		log_stderr("failure: fchmod");
> +		goto out;
> +	}
> +
> +	/* Verify that the sid bits got raised. */
> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
> +		log_stderr("failure: is_setgid");
> +		goto out;
> +	}
> +
> +	/* Changing mount properties on a detached mount. */
> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
> +	if (attr.userns_fd < 0) {
> +		log_stderr("failure: get_userns_fd");
> +		goto out;
> +	}
> +
> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
> +				     AT_EMPTY_PATH |
> +				     AT_NO_AUTOMOUNT |
> +				     AT_SYMLINK_NOFOLLOW |
> +				     OPEN_TREE_CLOEXEC |
> +				     OPEN_TREE_CLONE);
> +	if (open_tree_fd < 0) {
> +		log_stderr("failure: sys_open_tree");
> +		goto out;
> +	}
> +
> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
> +		log_stderr("failure: sys_mount_setattr");
> +		goto out;
> +	}
> +
> +	supported = openat_tmpfile_supported(open_tree_fd);
> +
> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
> +	 * whether has group execute or search permission.
> +	 */
> +	umask(S_IXGRP);
> +	mode = umask(S_IXGRP);
> +	if (!(mode & S_IXGRP))
> +		die("failure: umask");

All the calls to umask() in this patch should be after the fork() in the
child process. The die() helper is only supposed to be used in child
processes anyway. The rest looks fine to me. So with the umask() moved
you can add,
Tested-by: Christian Brauner (Microsoft) <[e-mail]>
Reviewed-by: Christian Brauner (Microsoft) <[e-mail]>

Christian Brauner Aug. 29, 2022, 1:52 p.m. UTC | #2

On Tue, Jul 26, 2022 at 05:31:21PM +0800, Yang Xu wrote:
> The current_umask() is stripped from the mode directly in the vfs if the
> filesystem either doesn't support acls or the filesystem has been
> mounted without posic acl support.
> 
> If the filesystem does support acls then current_umask() stripping is
> deferred to posix_acl_create(). So when the filesystem calls
> posix_acl_create() and there are no acls set or not supported then
> current_umask() will be stripped.
> 
> If the parent directory has a default acl then permissions are based off
> of that and current_umask() is ignored. Specifically, if the ACL has an
> ACL_MASK entry, the group permissions correspond to the permissions of
> the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
> group permissions correspond to the permissions of the ACL_GROUP_OBJ
> entry.
> 
> Here we only use setfacl to set default acl or add ACL_MASK to check
> whether inode strip  S_ISGID works correctly.
> 
> Like umask test, this patch is also designed to test kernel patchset behaviour
> "move S_ISGID stripping into the vfs* helper"
> 
> Signed-off-by: Yang Xu <[e-mail]>
> ---

Hey Yang,

Thank your for all that work! Just a few nits.

> 1.add kernel commit id
> 2.move umask into parent process intead of child process
> 3.remove duplicated comment for ACL_GROUP_OBJ and ACL_MASK because
> we have mentioned it before the function
>  src/vfs/idmapped-mounts.c | 704 ++++++++++++++++++++++++++++++++++++++
>  src/vfs/idmapped-mounts.h |   1 +
>  src/vfs/vfstest.c         | 345 ++++++++++++++++++-
>  tests/generic/999         |  33 ++
>  tests/generic/999.out     |   2 +
>  5 files changed, 1084 insertions(+), 1 deletion(-)
>  create mode 100755 tests/generic/999
>  create mode 100644 tests/generic/999.out
> 
> diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
> index f63ac44b..f934cf4a 100644
> --- a/src/vfs/idmapped-mounts.c
> +++ b/src/vfs/idmapped-mounts.c
> @@ -8083,6 +8083,700 @@ out:
>  	return fret;
>  }
>  
> +static int setgid_create_acl_idmapped(const struct vfstest_info *info)
> +{
> +	int fret = -1;
> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
> +	struct mount_attr attr = {
> +		.attr_set = MOUNT_ATTR_IDMAP,
> +	};
> +	pid_t pid;
> +	int tmpfile_fd = -EBADF;
> +	bool supported = false;
> +	char path[PATH_MAX];
> +	mode_t mode;
> +
> +	if (!caps_supported())
> +		return 0;
> +
> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
> +			      S_IWUSR |
> +			      S_IRGRP |
> +			      S_IWGRP |
> +			      S_IROTH |
> +			      S_IWOTH |
> +			      S_IXUSR |
> +			      S_IXGRP |
> +			      S_IXOTH |
> +			      S_ISGID), 0) {
> +		log_stderr("failure: fchmod");
> +		goto out;
> +	}
> +
> +	/* Verify that the sid bits got raised. */
> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
> +		log_stderr("failure: is_setgid");
> +		goto out;
> +	}
> +
> +	/* Changing mount properties on a detached mount. */
> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
> +	if (attr.userns_fd < 0) {
> +		log_stderr("failure: get_userns_fd");
> +		goto out;
> +	}
> +
> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
> +				     AT_EMPTY_PATH |
> +				     AT_NO_AUTOMOUNT |
> +				     AT_SYMLINK_NOFOLLOW |
> +				     OPEN_TREE_CLOEXEC |
> +				     OPEN_TREE_CLONE);
> +	if (open_tree_fd < 0) {
> +		log_stderr("failure: sys_open_tree");
> +		goto out;
> +	}
> +
> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
> +		log_stderr("failure: sys_mount_setattr");
> +		goto out;
> +	}
> +
> +	supported = openat_tmpfile_supported(open_tree_fd);
> +
> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
> +	 * whether has group execute or search permission.
> +	 */
> +	umask(S_IXGRP);
> +	mode = umask(S_IXGRP);
> +	if (!(mode & S_IXGRP))
> +		die("failure: umask");

Please move all the umask() calls after the fork() into the child.

> +
> +	pid = fork();
> +	if (pid < 0) {
> +		log_stderr("failure: fork");
> +		goto out;
> +	}
> +	if (pid == 0) {
> +		/* The group permissions correspond to the permissions of the
> +		 * ACL_MASK entry.
> +		 */
> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
> +		if (system(t_buf))
> +			die("failure: system");
> +
> +		if (!switch_ids(10000, 11000))
> +			die("failure: switch fsids");
> +
> +		/* create regular file via open() */
> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
> +		if (file1_fd < 0)
> +			die("failure: create");
> +
> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
> +		 * bit needs to be stripped.
> +		 */
> +		if (is_setgid(open_tree_fd, FILE1, 0))
> +			die("failure: is_setgid");
> +
> +		if (is_ixgrp(open_tree_fd, FILE1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create directory */
> +		if (mkdirat(open_tree_fd, DIR1, 0000))
> +			die("failure: create");
> +
> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
> +			/* We're not in_group_p(). */
> +			if (is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		} else {
> +			/* Directories always inherit the setgid bit. */
> +			if (!is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		}
> +
> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a special file via mknodat() vfs_create */
> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, FILE2, 0))
> +			die("failure: is_setgid");
> +
> +		if (is_ixgrp(open_tree_fd, FILE2, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a whiteout device via mknodat() vfs_mknod */
> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_setgid");
> +
> +		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/*
> +		 * In setgid directories newly created files always inherit the
> +		 * gid from the parent directory. Verify that the file is owned
> +		 * by gid 10000, not by gid 11000.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		/*
> +		 * In setgid directories newly created directories always
> +		 * inherit the gid from the parent directory. Verify that the
> +		 * directory is owned by gid 10000, not by gid 11000.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		if (unlinkat(open_tree_fd, FILE1, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, FILE2, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
> +			die("failure: delete");
> +
> +		/* create tmpfile via filesystem tmpfile api */
> +		if (supported) {
> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
> +			if (tmpfile_fd < 0)
> +				die("failure: create");
> +			/* link the temporary file into the filesystem, making it permanent */
> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
> +				die("failure: linkat");
> +			if (close(tmpfile_fd))
> +				die("failure: close");
> +			if (is_setgid(open_tree_fd, FILE3, 0))
> +				die("failure: is_setgid");
> +			if (is_ixgrp(open_tree_fd, FILE3, 0))
> +				die("failure: is_ixgrp");
> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
> +				die("failure: check ownership");
> +			if (unlinkat(open_tree_fd, FILE3, 0))
> +				die("failure: delete");
> +		}
> +
> +		exit(EXIT_SUCCESS);
> +	}
> +	if (wait_for_pid(pid))
> +		goto out;
> +
> +	pid = fork();
> +	if (pid < 0) {
> +		log_stderr("failure: fork");
> +		goto out;
> +	}
> +	if (pid == 0) {
> +		/* The group permissions correspond to the permissions of the
> +		 * ACL_GROUP_OBJ entry.
> +		 */
> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
> +		if (system(t_buf))
> +			die("failure: system");
> +
> +		if (!switch_ids(10000, 11000))
> +			die("failure: switch fsids");
> +
> +		/* create regular file via open() */
> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
> +		if (file1_fd < 0)
> +			die("failure: create");
> +
> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
> +		 * bit needs to be stripped.
> +		 */
> +		if (is_setgid(open_tree_fd, FILE1, 0))
> +			die("failure: is_setgid");
> +
> +		if (!is_ixgrp(open_tree_fd, FILE1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create directory */
> +		if (mkdirat(open_tree_fd, DIR1, 0000))
> +			die("failure: create");
> +
> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
> +			/* We're not in_group_p(). */
> +			if (is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		} else {
> +			/* Directories always inherit the setgid bit. */
> +			if (!is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		}
> +
> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a special file via mknodat() vfs_create */
> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, FILE2, 0))
> +			die("failure: is_setgid");
> +
> +		if (!is_ixgrp(open_tree_fd, FILE2, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a whiteout device via mknodat() vfs_mknod */
> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_setgid");
> +
> +		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/*
> +		 * In setgid directories newly created files always inherit the
> +		 * gid from the parent directory. Verify that the file is owned
> +		 * by gid 10000, not by gid 11000.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		/*
> +		 * In setgid directories newly created directories always
> +		 * inherit the gid from the parent directory. Verify that the
> +		 * directory is owned by gid 10000, not by gid 11000.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
> +			die("failure: check ownership");
> +
> +		if (unlinkat(open_tree_fd, FILE1, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, FILE2, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
> +			die("failure: delete");
> +
> +		/* create tmpfile via filesystem tmpfile api */
> +		if (supported) {
> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
> +			if (tmpfile_fd < 0)
> +				die("failure: create");
> +			/* link the temporary file into the filesystem, making it permanent */
> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
> +				die("failure: linkat");
> +			if (close(tmpfile_fd))
> +				die("failure: close");
> +			if (is_setgid(open_tree_fd, FILE3, 0))
> +				die("failure: is_setgid");
> +			if (!is_ixgrp(open_tree_fd, FILE3, 0))
> +				die("failure: is_ixgrp");
> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
> +				die("failure: check ownership");
> +			if (unlinkat(open_tree_fd, FILE3, 0))
> +				die("failure: delete");
> +		}
> +
> +		exit(EXIT_SUCCESS);
> +	}
> +	if (wait_for_pid(pid))
> +		goto out;
> +
> +	fret = 0;
> +	log_debug("Ran test");
> +out:
> +	safe_close(attr.userns_fd);
> +	safe_close(file1_fd);
> +	safe_close(open_tree_fd);
> +
> +	return fret;
> +}
> +
> +static int setgid_create_acl_idmapped_in_userns(const struct vfstest_info *info)
> +{
> +	int fret = -1;
> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
> +	struct mount_attr attr = {
> +		.attr_set = MOUNT_ATTR_IDMAP,
> +	};
> +	pid_t pid;
> +	int tmpfile_fd = -EBADF;
> +	bool supported = false;
> +	char path[PATH_MAX];
> +	mode_t mode;
> +
> +	if (!caps_supported())
> +		return 0;
> +
> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
> +			      S_IWUSR |
> +			      S_IRGRP |
> +			      S_IWGRP |
> +			      S_IROTH |
> +			      S_IWOTH |
> +			      S_IXUSR |
> +			      S_IXGRP |
> +			      S_IXOTH |
> +			      S_ISGID), 0) {
> +		log_stderr("failure: fchmod");
> +		goto out;
> +	}
> +
> +	/* Verify that the sid bits got raised. */
> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
> +		log_stderr("failure: is_setgid");
> +		goto out;
> +	}
> +
> +	/* Changing mount properties on a detached mount. */
> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
> +	if (attr.userns_fd < 0) {
> +		log_stderr("failure: get_userns_fd");
> +		goto out;
> +	}
> +
> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
> +				     AT_EMPTY_PATH |
> +				     AT_NO_AUTOMOUNT |
> +				     AT_SYMLINK_NOFOLLOW |
> +				     OPEN_TREE_CLOEXEC |
> +				     OPEN_TREE_CLONE);
> +	if (open_tree_fd < 0) {
> +		log_stderr("failure: sys_open_tree");
> +		goto out;
> +	}
> +
> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
> +		log_stderr("failure: sys_mount_setattr");
> +		goto out;
> +	}
> +
> +	supported = openat_tmpfile_supported(open_tree_fd);
> +
> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
> +	 * whether has group execute or search permission.
> +	 */
> +	umask(S_IXGRP);
> +	mode = umask(S_IXGRP);
> +	if (!(mode & S_IXGRP))
> +		die("failure: umask");
> +
> +	/*
> +	 * Below we verify that setgid inheritance for a newly created file or
> +	 * directory works correctly. As part of this we need to verify that
> +	 * newly created files or directories inherit their gid from their
> +	 * parent directory. So we change the parent directorie's gid to 1000
> +	 * and create a file with fs{g,u}id 0 and verify that the newly created
> +	 * file and directory inherit gid 1000, not 0.
> +	 */
> +	if (fchownat(info->t_dir1_fd, "", -1, 1000, AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) {
> +		log_stderr("failure: fchownat");
> +		goto out;
> +	}
> +
> +	pid = fork();
> +	if (pid < 0) {
> +		log_stderr("failure: fork");
> +		goto out;
> +	}
> +	if (pid == 0) {
> +		/* The group permissions correspond to the permissions of the
> +		 * ACL_MASK entry.
> +		 */
> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
> +		if (system(t_buf))
> +			die("failure: system");
> +
> +		if (!caps_supported()) {
> +			log_debug("skip: capability library not installed");
> +			exit(EXIT_SUCCESS);
> +		}
> +
> +		if (!switch_userns(attr.userns_fd, 0, 0, false))
> +			die("failure: switch_userns");
> +
> +		if (!caps_down_fsetid())
> +			die("failure: caps_down_fsetid");
> +
> +		/* create regular file via open() */
> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
> +		if (file1_fd < 0)
> +			die("failure: create");
> +
> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
> +		 * bit needs to be stripped.
> +		 */
> +		if (is_setgid(open_tree_fd, FILE1, 0))
> +			die("failure: is_setgid");
> +
> +		if (is_ixgrp(open_tree_fd, FILE1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create directory */
> +		if (mkdirat(open_tree_fd, DIR1, 0000))
> +			die("failure: create");
> +
> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
> +			/* We're not in_group_p(). */
> +			if (is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		} else {
> +			/* Directories always inherit the setgid bit. */
> +			if (!is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		}
> +
> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a special file via mknodat() vfs_create */
> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, FILE2, 0))
> +			die("failure: is_setgid");
> +
> +		if (is_ixgrp(open_tree_fd, FILE2, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a whiteout device via mknodat() vfs_mknod */
> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_setgid");
> +
> +		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/*
> +		 * In setgid directories newly created files always inherit the
> +		 * gid from the parent directory. Verify that the file is owned
> +		 * by gid 1000, not by gid 0.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		/*
> +		 * In setgid directories newly created directories always
> +		 * inherit the gid from the parent directory. Verify that the
> +		 * directory is owned by gid 1000, not by gid 0.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		if (unlinkat(open_tree_fd, FILE1, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, FILE2, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
> +			die("failure: delete");
> +
> +		/* create tmpfile via filesystem tmpfile api */
> +		if (supported) {
> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
> +			if (tmpfile_fd < 0)
> +				die("failure: create");
> +			/* link the temporary file into the filesystem, making it permanent */
> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
> +				die("failure: linkat");
> +			if (close(tmpfile_fd))
> +				die("failure: close");
> +			if (is_setgid(open_tree_fd, FILE3, 0))
> +				die("failure: is_setgid");
> +			if (is_ixgrp(open_tree_fd, FILE3, 0))
> +				die("failure: is_ixgrp");
> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
> +				die("failure: check ownership");
> +			if (unlinkat(open_tree_fd, FILE3, 0))
> +				die("failure: delete");
> +		}
> +
> +		exit(EXIT_SUCCESS);
> +	}
> +	if (wait_for_pid(pid))
> +		goto out;
> +
> +	pid = fork();
> +	if (pid < 0) {
> +		log_stderr("failure: fork");
> +		goto out;
> +	}
> +	if (pid == 0) {
> +		/* The group permissions correspond to the permissions of the
> +		 * ACL_GROUP_OBJ entry.
> +		 */
> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
> +		if (system(t_buf))
> +			die("failure: system");
> +
> +		if (!caps_supported()) {
> +			log_debug("skip: capability library not installed");
> +			exit(EXIT_SUCCESS);
> +		}
> +
> +		if (!switch_userns(attr.userns_fd, 0, 0, false))
> +			die("failure: switch_userns");
> +
> +		if (!caps_down_fsetid())
> +			die("failure: caps_down_fsetid");
> +
> +		/* create regular file via open() */
> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
> +		if (file1_fd < 0)
> +			die("failure: create");
> +
> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
> +		 * bit needs to be stripped.
> +		 */
> +		if (is_setgid(open_tree_fd, FILE1, 0))
> +			die("failure: is_setgid");
> +
> +		if (!is_ixgrp(open_tree_fd, FILE1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create directory */
> +		if (mkdirat(open_tree_fd, DIR1, 0000))
> +			die("failure: create");
> +
> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
> +			/* We're not in_group_p(). */
> +			if (is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		} else {
> +			/* Directories always inherit the setgid bit. */
> +			if (!is_setgid(open_tree_fd, DIR1, 0))
> +				die("failure: is_setgid");
> +		}
> +
> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
> +			die("failure: is_ixgrp");
> +
> +		/* create a special file via mknodat() vfs_create */
> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, FILE2, 0))
> +			die("failure: is_setgid");
> +
> +		if (!is_ixgrp(open_tree_fd, FILE2, 0))
> +			 die("failure: is_ixgrp");
> +		/* create a whiteout device via mknodat() vfs_mknod */
> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
> +			die("failure: mknodat");
> +
> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
> +			die("failure: is_setgid");
> +
> +		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
> +			 die("failure: is_ixgrp");
> +
> +		/*
> +		 * In setgid directories newly created files always inherit the
> +		 * gid from the parent directory. Verify that the file is owned
> +		 * by gid 1000, not by gid 0.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		/*
> +		 * In setgid directories newly created directories always
> +		 * inherit the gid from the parent directory. Verify that the
> +		 * directory is owned by gid 1000, not by gid 0.
> +		 */
> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
> +			die("failure: check ownership");
> +
> +		if (unlinkat(open_tree_fd, FILE1, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, FILE2, 0))
> +			die("failure: delete");
> +
> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
> +			die("failure: delete");
> +
> +		/* create tmpfile via filesystem tmpfile api */
> +		if (supported) {
> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
> +			if (tmpfile_fd < 0)
> +				die("failure: create");
> +			/* link the temporary file into the filesystem, making it permanent */
> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
> +				die("failure: linkat");
> +			if (close(tmpfile_fd))
> +				die("failure: close");
> +			if (is_setgid(open_tree_fd, FILE3, 0))
> +				die("failure: is_setgid");
> +			if (!is_ixgrp(open_tree_fd, FILE3, 0))
> +				die("failure: is_ixgrp");
> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
> +				die("failure: check ownership");
> +			if (unlinkat(open_tree_fd, FILE3, 0))
> +				die("failure: delete");
> +		}
> +
> +		exit(EXIT_SUCCESS);
> +	}
> +	if (wait_for_pid(pid))
> +		goto out;
> +
> +	fret = 0;
> +	log_debug("Ran test");
> +out:
> +	safe_close(attr.userns_fd);
> +	safe_close(file1_fd);
> +	safe_close(open_tree_fd);
> +
> +	return fret;
> +}
> +
>  static const struct test_struct t_idmapped_mounts[] = {
>  	{ acls,                                                         true,   "posix acls on regular mounts",                                                                 },
>  	{ create_in_userns,                                             true,   "create operations in user namespace",                                                          },
> @@ -8174,3 +8868,13 @@ const struct test_suite s_setgid_create_umask_idmapped_mounts = {
>  	.tests = t_setgid_create_umask_idmapped_mounts,
>  	.nr_tests = ARRAY_SIZE(t_setgid_create_umask_idmapped_mounts),
>  };
> +
> +static const struct test_struct t_setgid_create_acl_idmapped_mounts[] = {
> +	{ setgid_create_acl_idmapped,					T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount",                },
> +	{ setgid_create_acl_idmapped_in_userns,				T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount inside userns",  },
> +};
> +
> +const struct test_suite s_setgid_create_acl_idmapped_mounts = {
> +	.tests = t_setgid_create_acl_idmapped_mounts,
> +	.nr_tests = ARRAY_SIZE(t_setgid_create_acl_idmapped_mounts),
> +};
> diff --git a/src/vfs/idmapped-mounts.h b/src/vfs/idmapped-mounts.h
> index a9fb31ea..3b0f0825 100644
> --- a/src/vfs/idmapped-mounts.h
> +++ b/src/vfs/idmapped-mounts.h
> @@ -15,5 +15,6 @@ extern const struct test_suite s_nested_userns;
>  extern const struct test_suite s_setattr_fix_968219708108;
>  extern const struct test_suite s_setxattr_fix_705191b03d50;
>  extern const struct test_suite s_setgid_create_umask_idmapped_mounts;
> +extern const struct test_suite s_setgid_create_acl_idmapped_mounts;
>  
>  #endif /* __IDMAPPED_MOUNTS_H */
> diff --git a/src/vfs/vfstest.c b/src/vfs/vfstest.c
> index e928a1f5..f7639de3 100644
> --- a/src/vfs/vfstest.c
> +++ b/src/vfs/vfstest.c
> @@ -27,6 +27,8 @@
>  #include "missing.h"
>  #include "utils.h"
>  
> +static char t_buf[PATH_MAX];
> +
>  static void init_vfstest_info(struct vfstest_info *info)
>  {
>  	info->t_overflowuid		= 65534;
> @@ -1913,6 +1915,325 @@ out:
>  	return fret;
>  }
>  
> +/*
> + * If the parent directory has a default acl then permissions are based off
> + * of that and current_umask() is ignored. Specifically, if the ACL has an
> + * ACL_MASK entry, the group permissions correspond to the permissions of
> + * the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
> + * group permissions correspond to the permissions of the ACL_GROUP_OBJ
> + * entry.
> + *
> + * Use setfacl to check whether inode strip S_ISGID works correctly.
> + *
> + * Test for commit
> + * 1639a49ccdce ("fs: move S_ISGID stripping into the vfs_*() helpers").
> + */

This comment is pretty helpful and I'd like to see similar ones on top
of all the other tests you're adding. That would make it easier for
other to understand what's going on.

> +
> +static int setgid_create_acl(const struct vfstest_info *info)
> +{
> +	int fret = -1;
> +	int file1_fd = -EBADF;
> +	int tmpfile_fd = -EBADF;
> +	pid_t pid;
> +	bool supported = false;
> +	mode_t mode;
> +
> +	if (!caps_supported())
> +		return 0;
> +
> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
> +			      S_IWUSR |
> +			      S_IRGRP |
> +			      S_IWGRP |
> +			      S_IROTH |
> +			      S_IWOTH |
> +			      S_IXUSR |
> +			      S_IXGRP |
> +			      S_IXOTH |
> +			      S_ISGID), 0) {
> +		log_stderr("failure: fchmod");
> +		goto out;
> +	}
> +
> +	/* Verify that the setgid bit got raised. */
> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
> +		log_stderr("failure: is_setgid");
> +		goto out;
> +	}
> +
> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
> +
> +	umask(S_IXGRP);
> +	mode = umask(S_IXGRP);
> +	if (!(mode & S_IXGRP))
> +		die("failure: umask");
> +
> +	pid = fork();
> +	if (pid < 0) {
> +		log_stderr("failure: fork");
> +		goto out;
> +	}
> +	if (pid == 0) {
> +		/* The group permissions correspond to the permissions of the
> +		 * ACL_MASK entry.
> +		 */

It wouldn't hurt to add a longer comment to these setfacl calls
detailing what you're trying to test exactly otherwise it may be hard
for other who are not familiar with ACLs what this does. :)

> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
> +		if (system(t_buf))
> +			die("failure: system");

Other than that this looks good!
Christian

Yang Xu (Fujitsu) Aug. 30, 2022, 9:03 a.m. UTC | #3

on 2022/08/29 21:20, Christian Brauner wrote:
> On Tue, Jul 26, 2022 at 05:31:21PM +0800, Yang Xu wrote:
>> The current_umask() is stripped from the mode directly in the vfs if the
>> filesystem either doesn't support acls or the filesystem has been
>> mounted without posic acl support.
>>
>> If the filesystem does support acls then current_umask() stripping is
>> deferred to posix_acl_create(). So when the filesystem calls
>> posix_acl_create() and there are no acls set or not supported then
>> current_umask() will be stripped.
>>
>> If the parent directory has a default acl then permissions are based off
>> of that and current_umask() is ignored. Specifically, if the ACL has an
>> ACL_MASK entry, the group permissions correspond to the permissions of
>> the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
>> group permissions correspond to the permissions of the ACL_GROUP_OBJ
>> entry.
>>
>> Here we only use setfacl to set default acl or add ACL_MASK to check
>> whether inode strip  S_ISGID works correctly.
>>
>> Like umask test, this patch is also designed to test kernel patchset behaviour
>> "move S_ISGID stripping into the vfs* helper"
>>
>> Signed-off-by: Yang Xu <[e-mail]>
>> ---
> 
> Hey Yang,
> 
> Thanks for your patches! Just a minor comment below.
> 
>> 1.add kernel commit id
>> 2.move umask into parent process intead of child process
>> 3.remove duplicated comment for ACL_GROUP_OBJ and ACL_MASK because
>> we have mentioned it before the function
>>   src/vfs/idmapped-mounts.c | 704 ++++++++++++++++++++++++++++++++++++++
>>   src/vfs/idmapped-mounts.h |   1 +
>>   src/vfs/vfstest.c         | 345 ++++++++++++++++++-
>>   tests/generic/999         |  33 ++
>>   tests/generic/999.out     |   2 +
>>   5 files changed, 1084 insertions(+), 1 deletion(-)
>>   create mode 100755 tests/generic/999
>>   create mode 100644 tests/generic/999.out
>>
>> diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
>> index f63ac44b..f934cf4a 100644
>> --- a/src/vfs/idmapped-mounts.c
>> +++ b/src/vfs/idmapped-mounts.c
>> @@ -8083,6 +8083,700 @@ out:
>>   	return fret;
>>   }
>>   
>> +static int setgid_create_acl_idmapped(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
>> +	struct mount_attr attr = {
>> +		.attr_set = MOUNT_ATTR_IDMAP,
>> +	};
>> +	pid_t pid;
>> +	int tmpfile_fd = -EBADF;
>> +	bool supported = false;
>> +	char path[PATH_MAX];
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the sid bits got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	/* Changing mount properties on a detached mount. */
>> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
>> +	if (attr.userns_fd < 0) {
>> +		log_stderr("failure: get_userns_fd");
>> +		goto out;
>> +	}
>> +
>> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
>> +				     AT_EMPTY_PATH |
>> +				     AT_NO_AUTOMOUNT |
>> +				     AT_SYMLINK_NOFOLLOW |
>> +				     OPEN_TREE_CLOEXEC |
>> +				     OPEN_TREE_CLONE);
>> +	if (open_tree_fd < 0) {
>> +		log_stderr("failure: sys_open_tree");
>> +		goto out;
>> +	}
>> +
>> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
>> +		log_stderr("failure: sys_mount_setattr");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(open_tree_fd);
>> +
>> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
>> +	 * whether has group execute or search permission.
>> +	 */
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
> 
> All the calls to umask() in this patch should be after the fork() in the
> child process. The die() helper is only supposed to be used in child
> processes anyway.

Oh, yes, I did't notice it before. Will move it into child process on v3.

Best Regards
Yang Xu

> The rest looks fine to me. So with the umask() moved
> you can add,
> Tested-by: Christian Brauner (Microsoft) <[e-mail]>
> Reviewed-by: Christian Brauner (Microsoft) <[e-mail]>

Yang Xu (Fujitsu) Aug. 30, 2022, 9:06 a.m. UTC | #4

on 2022/08/29 21:52, Christian Brauner wrote:
> On Tue, Jul 26, 2022 at 05:31:21PM +0800, Yang Xu wrote:
>> The current_umask() is stripped from the mode directly in the vfs if the
>> filesystem either doesn't support acls or the filesystem has been
>> mounted without posic acl support.
>>
>> If the filesystem does support acls then current_umask() stripping is
>> deferred to posix_acl_create(). So when the filesystem calls
>> posix_acl_create() and there are no acls set or not supported then
>> current_umask() will be stripped.
>>
>> If the parent directory has a default acl then permissions are based off
>> of that and current_umask() is ignored. Specifically, if the ACL has an
>> ACL_MASK entry, the group permissions correspond to the permissions of
>> the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
>> group permissions correspond to the permissions of the ACL_GROUP_OBJ
>> entry.
>>
>> Here we only use setfacl to set default acl or add ACL_MASK to check
>> whether inode strip  S_ISGID works correctly.
>>
>> Like umask test, this patch is also designed to test kernel patchset behaviour
>> "move S_ISGID stripping into the vfs* helper"
>>
>> Signed-off-by: Yang Xu <[e-mail]>
>> ---
> 
> Hey Yang,
> 
> Thank your for all that work! Just a few nits.
> 
>> 1.add kernel commit id
>> 2.move umask into parent process intead of child process
>> 3.remove duplicated comment for ACL_GROUP_OBJ and ACL_MASK because
>> we have mentioned it before the function
>>   src/vfs/idmapped-mounts.c | 704 ++++++++++++++++++++++++++++++++++++++
>>   src/vfs/idmapped-mounts.h |   1 +
>>   src/vfs/vfstest.c         | 345 ++++++++++++++++++-
>>   tests/generic/999         |  33 ++
>>   tests/generic/999.out     |   2 +
>>   5 files changed, 1084 insertions(+), 1 deletion(-)
>>   create mode 100755 tests/generic/999
>>   create mode 100644 tests/generic/999.out
>>
>> diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
>> index f63ac44b..f934cf4a 100644
>> --- a/src/vfs/idmapped-mounts.c
>> +++ b/src/vfs/idmapped-mounts.c
>> @@ -8083,6 +8083,700 @@ out:
>>   	return fret;
>>   }
>>   
>> +static int setgid_create_acl_idmapped(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
>> +	struct mount_attr attr = {
>> +		.attr_set = MOUNT_ATTR_IDMAP,
>> +	};
>> +	pid_t pid;
>> +	int tmpfile_fd = -EBADF;
>> +	bool supported = false;
>> +	char path[PATH_MAX];
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the sid bits got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	/* Changing mount properties on a detached mount. */
>> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
>> +	if (attr.userns_fd < 0) {
>> +		log_stderr("failure: get_userns_fd");
>> +		goto out;
>> +	}
>> +
>> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
>> +				     AT_EMPTY_PATH |
>> +				     AT_NO_AUTOMOUNT |
>> +				     AT_SYMLINK_NOFOLLOW |
>> +				     OPEN_TREE_CLOEXEC |
>> +				     OPEN_TREE_CLONE);
>> +	if (open_tree_fd < 0) {
>> +		log_stderr("failure: sys_open_tree");
>> +		goto out;
>> +	}
>> +
>> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
>> +		log_stderr("failure: sys_mount_setattr");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(open_tree_fd);
>> +
>> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
>> +	 * whether has group execute or search permission.
>> +	 */
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
> 
> Please move all the umask() calls after the fork() into the child.

OK.
> 
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_MASK entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!switch_ids(10000, 11000))
>> +			die("failure: switch fsids");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE2, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_GROUP_OBJ entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!switch_ids(10000, 11000))
>> +			die("failure: switch fsids");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE2, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (!is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	fret = 0;
>> +	log_debug("Ran test");
>> +out:
>> +	safe_close(attr.userns_fd);
>> +	safe_close(file1_fd);
>> +	safe_close(open_tree_fd);
>> +
>> +	return fret;
>> +}
>> +
>> +static int setgid_create_acl_idmapped_in_userns(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
>> +	struct mount_attr attr = {
>> +		.attr_set = MOUNT_ATTR_IDMAP,
>> +	};
>> +	pid_t pid;
>> +	int tmpfile_fd = -EBADF;
>> +	bool supported = false;
>> +	char path[PATH_MAX];
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the sid bits got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	/* Changing mount properties on a detached mount. */
>> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
>> +	if (attr.userns_fd < 0) {
>> +		log_stderr("failure: get_userns_fd");
>> +		goto out;
>> +	}
>> +
>> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
>> +				     AT_EMPTY_PATH |
>> +				     AT_NO_AUTOMOUNT |
>> +				     AT_SYMLINK_NOFOLLOW |
>> +				     OPEN_TREE_CLOEXEC |
>> +				     OPEN_TREE_CLONE);
>> +	if (open_tree_fd < 0) {
>> +		log_stderr("failure: sys_open_tree");
>> +		goto out;
>> +	}
>> +
>> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
>> +		log_stderr("failure: sys_mount_setattr");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(open_tree_fd);
>> +
>> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
>> +	 * whether has group execute or search permission.
>> +	 */
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
>> +
>> +	/*
>> +	 * Below we verify that setgid inheritance for a newly created file or
>> +	 * directory works correctly. As part of this we need to verify that
>> +	 * newly created files or directories inherit their gid from their
>> +	 * parent directory. So we change the parent directorie's gid to 1000
>> +	 * and create a file with fs{g,u}id 0 and verify that the newly created
>> +	 * file and directory inherit gid 1000, not 0.
>> +	 */
>> +	if (fchownat(info->t_dir1_fd, "", -1, 1000, AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) {
>> +		log_stderr("failure: fchownat");
>> +		goto out;
>> +	}
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_MASK entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!caps_supported()) {
>> +			log_debug("skip: capability library not installed");
>> +			exit(EXIT_SUCCESS);
>> +		}
>> +
>> +		if (!switch_userns(attr.userns_fd, 0, 0, false))
>> +			die("failure: switch_userns");
>> +
>> +		if (!caps_down_fsetid())
>> +			die("failure: caps_down_fsetid");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE2, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_GROUP_OBJ entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!caps_supported()) {
>> +			log_debug("skip: capability library not installed");
>> +			exit(EXIT_SUCCESS);
>> +		}
>> +
>> +		if (!switch_userns(attr.userns_fd, 0, 0, false))
>> +			die("failure: switch_userns");
>> +
>> +		if (!caps_down_fsetid())
>> +			die("failure: caps_down_fsetid");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE2, 0))
>> +			 die("failure: is_ixgrp");
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			 die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (!is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	fret = 0;
>> +	log_debug("Ran test");
>> +out:
>> +	safe_close(attr.userns_fd);
>> +	safe_close(file1_fd);
>> +	safe_close(open_tree_fd);
>> +
>> +	return fret;
>> +}
>> +
>>   static const struct test_struct t_idmapped_mounts[] = {
>>   	{ acls,                                                         true,   "posix acls on regular mounts",                                                                 },
>>   	{ create_in_userns,                                             true,   "create operations in user namespace",                                                          },
>> @@ -8174,3 +8868,13 @@ const struct test_suite s_setgid_create_umask_idmapped_mounts = {
>>   	.tests = t_setgid_create_umask_idmapped_mounts,
>>   	.nr_tests = ARRAY_SIZE(t_setgid_create_umask_idmapped_mounts),
>>   };
>> +
>> +static const struct test_struct t_setgid_create_acl_idmapped_mounts[] = {
>> +	{ setgid_create_acl_idmapped,					T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount",                },
>> +	{ setgid_create_acl_idmapped_in_userns,				T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount inside userns",  },
>> +};
>> +
>> +const struct test_suite s_setgid_create_acl_idmapped_mounts = {
>> +	.tests = t_setgid_create_acl_idmapped_mounts,
>> +	.nr_tests = ARRAY_SIZE(t_setgid_create_acl_idmapped_mounts),
>> +};
>> diff --git a/src/vfs/idmapped-mounts.h b/src/vfs/idmapped-mounts.h
>> index a9fb31ea..3b0f0825 100644
>> --- a/src/vfs/idmapped-mounts.h
>> +++ b/src/vfs/idmapped-mounts.h
>> @@ -15,5 +15,6 @@ extern const struct test_suite s_nested_userns;
>>   extern const struct test_suite s_setattr_fix_968219708108;
>>   extern const struct test_suite s_setxattr_fix_705191b03d50;
>>   extern const struct test_suite s_setgid_create_umask_idmapped_mounts;
>> +extern const struct test_suite s_setgid_create_acl_idmapped_mounts;
>>   
>>   #endif /* __IDMAPPED_MOUNTS_H */
>> diff --git a/src/vfs/vfstest.c b/src/vfs/vfstest.c
>> index e928a1f5..f7639de3 100644
>> --- a/src/vfs/vfstest.c
>> +++ b/src/vfs/vfstest.c
>> @@ -27,6 +27,8 @@
>>   #include "missing.h"
>>   #include "utils.h"
>>   
>> +static char t_buf[PATH_MAX];
>> +
>>   static void init_vfstest_info(struct vfstest_info *info)
>>   {
>>   	info->t_overflowuid		= 65534;
>> @@ -1913,6 +1915,325 @@ out:
>>   	return fret;
>>   }
>>   
>> +/*
>> + * If the parent directory has a default acl then permissions are based off
>> + * of that and current_umask() is ignored. Specifically, if the ACL has an
>> + * ACL_MASK entry, the group permissions correspond to the permissions of
>> + * the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
>> + * group permissions correspond to the permissions of the ACL_GROUP_OBJ
>> + * entry.
>> + *
>> + * Use setfacl to check whether inode strip S_ISGID works correctly.
>> + *
>> + * Test for commit
>> + * 1639a49ccdce ("fs: move S_ISGID stripping into the vfs_*() helpers").
>> + */
> 
> This comment is pretty helpful and I'd like to see similar ones on top
> of all the other tests you're adding. That would make it easier for
> other to understand what's going on.

OK.
> 
>> +
>> +static int setgid_create_acl(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF;
>> +	int tmpfile_fd = -EBADF;
>> +	pid_t pid;
>> +	bool supported = false;
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the setgid bit got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>> +
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_MASK entry.
>> +		 */
> 
> It wouldn't hurt to add a longer comment to these setfacl calls
> detailing what you're trying to test exactly otherwise it may be hard
> for other who are not familiar with ACLs what this does. :)

Yes, will add a longer comment.

Best Regards
Yang Xu
> 
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
> 
> Other than that this looks good!
> Christian

Patch

diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
index f63ac44b..f934cf4a 100644
--- a/src/vfs/idmapped-mounts.c
+++ b/src/vfs/idmapped-mounts.c
@@ -8083,6 +8083,700 @@  out:
 	return fret;
 }
 
+static int setgid_create_acl_idmapped(const struct vfstest_info *info)
+{
+	int fret = -1;
+	int file1_fd = -EBADF, open_tree_fd = -EBADF;
+	struct mount_attr attr = {
+		.attr_set = MOUNT_ATTR_IDMAP,
+	};
+	pid_t pid;
+	int tmpfile_fd = -EBADF;
+	bool supported = false;
+	char path[PATH_MAX];
+	mode_t mode;
+
+	if (!caps_supported())
+		return 0;
+
+	if (fchmod(info->t_dir1_fd, S_IRUSR |
+			      S_IWUSR |
+			      S_IRGRP |
+			      S_IWGRP |
+			      S_IROTH |
+			      S_IWOTH |
+			      S_IXUSR |
+			      S_IXGRP |
+			      S_IXOTH |
+			      S_ISGID), 0) {
+		log_stderr("failure: fchmod");
+		goto out;
+	}
+
+	/* Verify that the sid bits got raised. */
+	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
+		log_stderr("failure: is_setgid");
+		goto out;
+	}
+
+	/* Changing mount properties on a detached mount. */
+	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
+	if (attr.userns_fd < 0) {
+		log_stderr("failure: get_userns_fd");
+		goto out;
+	}
+
+	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
+				     AT_EMPTY_PATH |
+				     AT_NO_AUTOMOUNT |
+				     AT_SYMLINK_NOFOLLOW |
+				     OPEN_TREE_CLOEXEC |
+				     OPEN_TREE_CLONE);
+	if (open_tree_fd < 0) {
+		log_stderr("failure: sys_open_tree");
+		goto out;
+	}
+
+	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
+		log_stderr("failure: sys_mount_setattr");
+		goto out;
+	}
+
+	supported = openat_tmpfile_supported(open_tree_fd);
+
+	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
+	 * whether has group execute or search permission.
+	 */
+	umask(S_IXGRP);
+	mode = umask(S_IXGRP);
+	if (!(mode & S_IXGRP))
+		die("failure: umask");
+
+	pid = fork();
+	if (pid < 0) {
+		log_stderr("failure: fork");
+		goto out;
+	}
+	if (pid == 0) {
+		/* The group permissions correspond to the permissions of the
+		 * ACL_MASK entry.
+		 */
+		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
+		if (system(t_buf))
+			die("failure: system");
+
+		if (!switch_ids(10000, 11000))
+			die("failure: switch fsids");
+
+		/* create regular file via open() */
+		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
+		if (file1_fd < 0)
+			die("failure: create");
+
+		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
+		 * bit needs to be stripped.
+		 */
+		if (is_setgid(open_tree_fd, FILE1, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(open_tree_fd, FILE1, 0))
+			die("failure: is_ixgrp");
+
+		/* create directory */
+		if (mkdirat(open_tree_fd, DIR1, 0000))
+			die("failure: create");
+
+		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
+			/* We're not in_group_p(). */
+			if (is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		} else {
+			/* Directories always inherit the setgid bit. */
+			if (!is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		}
+
+		if (is_ixgrp(open_tree_fd, DIR1, 0))
+			die("failure: is_ixgrp");
+
+		/* create a special file via mknodat() vfs_create */
+		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, FILE2, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(open_tree_fd, FILE2, 0))
+			die("failure: is_ixgrp");
+
+		/* create a whiteout device via mknodat() vfs_mknod */
+		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_ixgrp");
+
+		/*
+		 * In setgid directories newly created files always inherit the
+		 * gid from the parent directory. Verify that the file is owned
+		 * by gid 10000, not by gid 11000.
+		 */
+		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		/*
+		 * In setgid directories newly created directories always
+		 * inherit the gid from the parent directory. Verify that the
+		 * directory is owned by gid 10000, not by gid 11000.
+		 */
+		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		if (unlinkat(open_tree_fd, FILE1, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, FILE2, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, CHRDEV1, 0))
+			die("failure: delete");
+
+		/* create tmpfile via filesystem tmpfile api */
+		if (supported) {
+			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
+			if (tmpfile_fd < 0)
+				die("failure: create");
+			/* link the temporary file into the filesystem, making it permanent */
+			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
+			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
+				die("failure: linkat");
+			if (close(tmpfile_fd))
+				die("failure: close");
+			if (is_setgid(open_tree_fd, FILE3, 0))
+				die("failure: is_setgid");
+			if (is_ixgrp(open_tree_fd, FILE3, 0))
+				die("failure: is_ixgrp");
+			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
+				die("failure: check ownership");
+			if (unlinkat(open_tree_fd, FILE3, 0))
+				die("failure: delete");
+		}
+
+		exit(EXIT_SUCCESS);
+	}
+	if (wait_for_pid(pid))
+		goto out;
+
+	pid = fork();
+	if (pid < 0) {
+		log_stderr("failure: fork");
+		goto out;
+	}
+	if (pid == 0) {
+		/* The group permissions correspond to the permissions of the
+		 * ACL_GROUP_OBJ entry.
+		 */
+		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
+		if (system(t_buf))
+			die("failure: system");
+
+		if (!switch_ids(10000, 11000))
+			die("failure: switch fsids");
+
+		/* create regular file via open() */
+		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
+		if (file1_fd < 0)
+			die("failure: create");
+
+		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
+		 * bit needs to be stripped.
+		 */
+		if (is_setgid(open_tree_fd, FILE1, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(open_tree_fd, FILE1, 0))
+			die("failure: is_ixgrp");
+
+		/* create directory */
+		if (mkdirat(open_tree_fd, DIR1, 0000))
+			die("failure: create");
+
+		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
+			/* We're not in_group_p(). */
+			if (is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		} else {
+			/* Directories always inherit the setgid bit. */
+			if (!is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		}
+
+		if (is_ixgrp(open_tree_fd, DIR1, 0))
+			die("failure: is_ixgrp");
+
+		/* create a special file via mknodat() vfs_create */
+		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, FILE2, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(open_tree_fd, FILE2, 0))
+			die("failure: is_ixgrp");
+
+		/* create a whiteout device via mknodat() vfs_mknod */
+		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_ixgrp");
+
+		/*
+		 * In setgid directories newly created files always inherit the
+		 * gid from the parent directory. Verify that the file is owned
+		 * by gid 10000, not by gid 11000.
+		 */
+		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		/*
+		 * In setgid directories newly created directories always
+		 * inherit the gid from the parent directory. Verify that the
+		 * directory is owned by gid 10000, not by gid 11000.
+		 */
+		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
+			die("failure: check ownership");
+
+		if (unlinkat(open_tree_fd, FILE1, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, FILE2, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, CHRDEV1, 0))
+			die("failure: delete");
+
+		/* create tmpfile via filesystem tmpfile api */
+		if (supported) {
+			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
+			if (tmpfile_fd < 0)
+				die("failure: create");
+			/* link the temporary file into the filesystem, making it permanent */
+			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
+			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
+				die("failure: linkat");
+			if (close(tmpfile_fd))
+				die("failure: close");
+			if (is_setgid(open_tree_fd, FILE3, 0))
+				die("failure: is_setgid");
+			if (!is_ixgrp(open_tree_fd, FILE3, 0))
+				die("failure: is_ixgrp");
+			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
+				die("failure: check ownership");
+			if (unlinkat(open_tree_fd, FILE3, 0))
+				die("failure: delete");
+		}
+
+		exit(EXIT_SUCCESS);
+	}
+	if (wait_for_pid(pid))
+		goto out;
+
+	fret = 0;
+	log_debug("Ran test");
+out:
+	safe_close(attr.userns_fd);
+	safe_close(file1_fd);
+	safe_close(open_tree_fd);
+
+	return fret;
+}
+
+static int setgid_create_acl_idmapped_in_userns(const struct vfstest_info *info)
+{
+	int fret = -1;
+	int file1_fd = -EBADF, open_tree_fd = -EBADF;
+	struct mount_attr attr = {
+		.attr_set = MOUNT_ATTR_IDMAP,
+	};
+	pid_t pid;
+	int tmpfile_fd = -EBADF;
+	bool supported = false;
+	char path[PATH_MAX];
+	mode_t mode;
+
+	if (!caps_supported())
+		return 0;
+
+	if (fchmod(info->t_dir1_fd, S_IRUSR |
+			      S_IWUSR |
+			      S_IRGRP |
+			      S_IWGRP |
+			      S_IROTH |
+			      S_IWOTH |
+			      S_IXUSR |
+			      S_IXGRP |
+			      S_IXOTH |
+			      S_ISGID), 0) {
+		log_stderr("failure: fchmod");
+		goto out;
+	}
+
+	/* Verify that the sid bits got raised. */
+	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
+		log_stderr("failure: is_setgid");
+		goto out;
+	}
+
+	/* Changing mount properties on a detached mount. */
+	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
+	if (attr.userns_fd < 0) {
+		log_stderr("failure: get_userns_fd");
+		goto out;
+	}
+
+	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
+				     AT_EMPTY_PATH |
+				     AT_NO_AUTOMOUNT |
+				     AT_SYMLINK_NOFOLLOW |
+				     OPEN_TREE_CLOEXEC |
+				     OPEN_TREE_CLONE);
+	if (open_tree_fd < 0) {
+		log_stderr("failure: sys_open_tree");
+		goto out;
+	}
+
+	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
+		log_stderr("failure: sys_mount_setattr");
+		goto out;
+	}
+
+	supported = openat_tmpfile_supported(open_tree_fd);
+
+	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
+	 * whether has group execute or search permission.
+	 */
+	umask(S_IXGRP);
+	mode = umask(S_IXGRP);
+	if (!(mode & S_IXGRP))
+		die("failure: umask");
+
+	/*
+	 * Below we verify that setgid inheritance for a newly created file or
+	 * directory works correctly. As part of this we need to verify that
+	 * newly created files or directories inherit their gid from their
+	 * parent directory. So we change the parent directorie's gid to 1000
+	 * and create a file with fs{g,u}id 0 and verify that the newly created
+	 * file and directory inherit gid 1000, not 0.
+	 */
+	if (fchownat(info->t_dir1_fd, "", -1, 1000, AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) {
+		log_stderr("failure: fchownat");
+		goto out;
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		log_stderr("failure: fork");
+		goto out;
+	}
+	if (pid == 0) {
+		/* The group permissions correspond to the permissions of the
+		 * ACL_MASK entry.
+		 */
+		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
+		if (system(t_buf))
+			die("failure: system");
+
+		if (!caps_supported()) {
+			log_debug("skip: capability library not installed");
+			exit(EXIT_SUCCESS);
+		}
+
+		if (!switch_userns(attr.userns_fd, 0, 0, false))
+			die("failure: switch_userns");
+
+		if (!caps_down_fsetid())
+			die("failure: caps_down_fsetid");
+
+		/* create regular file via open() */
+		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
+		if (file1_fd < 0)
+			die("failure: create");
+
+		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
+		 * bit needs to be stripped.
+		 */
+		if (is_setgid(open_tree_fd, FILE1, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(open_tree_fd, FILE1, 0))
+			die("failure: is_ixgrp");
+
+		/* create directory */
+		if (mkdirat(open_tree_fd, DIR1, 0000))
+			die("failure: create");
+
+		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
+			/* We're not in_group_p(). */
+			if (is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		} else {
+			/* Directories always inherit the setgid bit. */
+			if (!is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		}
+
+		if (is_ixgrp(open_tree_fd, DIR1, 0))
+			die("failure: is_ixgrp");
+
+		/* create a special file via mknodat() vfs_create */
+		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, FILE2, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(open_tree_fd, FILE2, 0))
+			die("failure: is_ixgrp");
+
+		/* create a whiteout device via mknodat() vfs_mknod */
+		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_ixgrp");
+
+		/*
+		 * In setgid directories newly created files always inherit the
+		 * gid from the parent directory. Verify that the file is owned
+		 * by gid 1000, not by gid 0.
+		 */
+		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
+			die("failure: check ownership");
+
+		/*
+		 * In setgid directories newly created directories always
+		 * inherit the gid from the parent directory. Verify that the
+		 * directory is owned by gid 1000, not by gid 0.
+		 */
+		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
+			die("failure: check ownership");
+
+		if (unlinkat(open_tree_fd, FILE1, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, FILE2, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, CHRDEV1, 0))
+			die("failure: delete");
+
+		/* create tmpfile via filesystem tmpfile api */
+		if (supported) {
+			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
+			if (tmpfile_fd < 0)
+				die("failure: create");
+			/* link the temporary file into the filesystem, making it permanent */
+			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
+			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
+				die("failure: linkat");
+			if (close(tmpfile_fd))
+				die("failure: close");
+			if (is_setgid(open_tree_fd, FILE3, 0))
+				die("failure: is_setgid");
+			if (is_ixgrp(open_tree_fd, FILE3, 0))
+				die("failure: is_ixgrp");
+			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
+				die("failure: check ownership");
+			if (unlinkat(open_tree_fd, FILE3, 0))
+				die("failure: delete");
+		}
+
+		exit(EXIT_SUCCESS);
+	}
+	if (wait_for_pid(pid))
+		goto out;
+
+	pid = fork();
+	if (pid < 0) {
+		log_stderr("failure: fork");
+		goto out;
+	}
+	if (pid == 0) {
+		/* The group permissions correspond to the permissions of the
+		 * ACL_GROUP_OBJ entry.
+		 */
+		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
+		if (system(t_buf))
+			die("failure: system");
+
+		if (!caps_supported()) {
+			log_debug("skip: capability library not installed");
+			exit(EXIT_SUCCESS);
+		}
+
+		if (!switch_userns(attr.userns_fd, 0, 0, false))
+			die("failure: switch_userns");
+
+		if (!caps_down_fsetid())
+			die("failure: caps_down_fsetid");
+
+		/* create regular file via open() */
+		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
+		if (file1_fd < 0)
+			die("failure: create");
+
+		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
+		 * bit needs to be stripped.
+		 */
+		if (is_setgid(open_tree_fd, FILE1, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(open_tree_fd, FILE1, 0))
+			die("failure: is_ixgrp");
+
+		/* create directory */
+		if (mkdirat(open_tree_fd, DIR1, 0000))
+			die("failure: create");
+
+		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
+			/* We're not in_group_p(). */
+			if (is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		} else {
+			/* Directories always inherit the setgid bit. */
+			if (!is_setgid(open_tree_fd, DIR1, 0))
+				die("failure: is_setgid");
+		}
+
+		if (is_ixgrp(open_tree_fd, DIR1, 0))
+			die("failure: is_ixgrp");
+
+		/* create a special file via mknodat() vfs_create */
+		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, FILE2, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(open_tree_fd, FILE2, 0))
+			 die("failure: is_ixgrp");
+		/* create a whiteout device via mknodat() vfs_mknod */
+		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(open_tree_fd, CHRDEV1, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
+			 die("failure: is_ixgrp");
+
+		/*
+		 * In setgid directories newly created files always inherit the
+		 * gid from the parent directory. Verify that the file is owned
+		 * by gid 1000, not by gid 0.
+		 */
+		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
+			die("failure: check ownership");
+
+		/*
+		 * In setgid directories newly created directories always
+		 * inherit the gid from the parent directory. Verify that the
+		 * directory is owned by gid 1000, not by gid 0.
+		 */
+		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
+			die("failure: check ownership");
+
+		if (unlinkat(open_tree_fd, FILE1, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, FILE2, 0))
+			die("failure: delete");
+
+		if (unlinkat(open_tree_fd, CHRDEV1, 0))
+			die("failure: delete");
+
+		/* create tmpfile via filesystem tmpfile api */
+		if (supported) {
+			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
+			if (tmpfile_fd < 0)
+				die("failure: create");
+			/* link the temporary file into the filesystem, making it permanent */
+			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
+			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
+				die("failure: linkat");
+			if (close(tmpfile_fd))
+				die("failure: close");
+			if (is_setgid(open_tree_fd, FILE3, 0))
+				die("failure: is_setgid");
+			if (!is_ixgrp(open_tree_fd, FILE3, 0))
+				die("failure: is_ixgrp");
+			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
+				die("failure: check ownership");
+			if (unlinkat(open_tree_fd, FILE3, 0))
+				die("failure: delete");
+		}
+
+		exit(EXIT_SUCCESS);
+	}
+	if (wait_for_pid(pid))
+		goto out;
+
+	fret = 0;
+	log_debug("Ran test");
+out:
+	safe_close(attr.userns_fd);
+	safe_close(file1_fd);
+	safe_close(open_tree_fd);
+
+	return fret;
+}
+
 static const struct test_struct t_idmapped_mounts[] = {
 	{ acls,                                                         true,   "posix acls on regular mounts",                                                                 },
 	{ create_in_userns,                                             true,   "create operations in user namespace",                                                          },
@@ -8174,3 +8868,13 @@  const struct test_suite s_setgid_create_umask_idmapped_mounts = {
 	.tests = t_setgid_create_umask_idmapped_mounts,
 	.nr_tests = ARRAY_SIZE(t_setgid_create_umask_idmapped_mounts),
 };
+
+static const struct test_struct t_setgid_create_acl_idmapped_mounts[] = {
+	{ setgid_create_acl_idmapped,					T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount",                },
+	{ setgid_create_acl_idmapped_in_userns,				T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount inside userns",  },
+};
+
+const struct test_suite s_setgid_create_acl_idmapped_mounts = {
+	.tests = t_setgid_create_acl_idmapped_mounts,
+	.nr_tests = ARRAY_SIZE(t_setgid_create_acl_idmapped_mounts),
+};
diff --git a/src/vfs/idmapped-mounts.h b/src/vfs/idmapped-mounts.h
index a9fb31ea..3b0f0825 100644
--- a/src/vfs/idmapped-mounts.h
+++ b/src/vfs/idmapped-mounts.h
@@ -15,5 +15,6 @@  extern const struct test_suite s_nested_userns;
 extern const struct test_suite s_setattr_fix_968219708108;
 extern const struct test_suite s_setxattr_fix_705191b03d50;
 extern const struct test_suite s_setgid_create_umask_idmapped_mounts;
+extern const struct test_suite s_setgid_create_acl_idmapped_mounts;
 
 #endif /* __IDMAPPED_MOUNTS_H */
diff --git a/src/vfs/vfstest.c b/src/vfs/vfstest.c
index e928a1f5..f7639de3 100644
--- a/src/vfs/vfstest.c
+++ b/src/vfs/vfstest.c
@@ -27,6 +27,8 @@ 
 #include "missing.h"
 #include "utils.h"
 
+static char t_buf[PATH_MAX];
+
 static void init_vfstest_info(struct vfstest_info *info)
 {
 	info->t_overflowuid		= 65534;
@@ -1913,6 +1915,325 @@  out:
 	return fret;
 }
 
+/*
+ * If the parent directory has a default acl then permissions are based off
+ * of that and current_umask() is ignored. Specifically, if the ACL has an
+ * ACL_MASK entry, the group permissions correspond to the permissions of
+ * the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
+ * group permissions correspond to the permissions of the ACL_GROUP_OBJ
+ * entry.
+ *
+ * Use setfacl to check whether inode strip S_ISGID works correctly.
+ *
+ * Test for commit
+ * 1639a49ccdce ("fs: move S_ISGID stripping into the vfs_*() helpers").
+ */
+
+static int setgid_create_acl(const struct vfstest_info *info)
+{
+	int fret = -1;
+	int file1_fd = -EBADF;
+	int tmpfile_fd = -EBADF;
+	pid_t pid;
+	bool supported = false;
+	mode_t mode;
+
+	if (!caps_supported())
+		return 0;
+
+	if (fchmod(info->t_dir1_fd, S_IRUSR |
+			      S_IWUSR |
+			      S_IRGRP |
+			      S_IWGRP |
+			      S_IROTH |
+			      S_IWOTH |
+			      S_IXUSR |
+			      S_IXGRP |
+			      S_IXOTH |
+			      S_ISGID), 0) {
+		log_stderr("failure: fchmod");
+		goto out;
+	}
+
+	/* Verify that the setgid bit got raised. */
+	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
+		log_stderr("failure: is_setgid");
+		goto out;
+	}
+
+	supported = openat_tmpfile_supported(info->t_dir1_fd);
+
+	umask(S_IXGRP);
+	mode = umask(S_IXGRP);
+	if (!(mode & S_IXGRP))
+		die("failure: umask");
+
+	pid = fork();
+	if (pid < 0) {
+		log_stderr("failure: fork");
+		goto out;
+	}
+	if (pid == 0) {
+		/* The group permissions correspond to the permissions of the
+		 * ACL_MASK entry.
+		 */
+		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
+		if (system(t_buf))
+			die("failure: system");
+
+		if (!switch_ids(0, 10000))
+			die("failure: switch_ids");
+
+		if (!caps_down_fsetid())
+			die("failure: caps_down_fsetid");
+
+		/* create regular file via open() */
+		file1_fd = openat(info->t_dir1_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
+		if (file1_fd < 0)
+			die("failure: create");
+
+		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
+		 * bit needs to be stripped.
+		 */
+		if (is_setgid(info->t_dir1_fd, FILE1, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(info->t_dir1_fd, FILE1, 0))
+			die("failure: is_ixgrp");
+
+		/* create directory */
+		if (mkdirat(info->t_dir1_fd, DIR1, 0000))
+			die("failure: create");
+
+		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
+			/* We're not in_group_p(). */
+			if (is_setgid(info->t_dir1_fd, DIR1, 0))
+				die("failure: is_setgid");
+		} else {
+			/* Directories always inherit the setgid bit. */
+			if (!is_setgid(info->t_dir1_fd, DIR1, 0))
+				die("failure: is_setgid");
+		}
+
+		if (is_ixgrp(info->t_dir1_fd, DIR1, 0))
+			die("failure: is_ixgrp");
+
+		/* create a special file via mknodat() vfs_create */
+		if (mknodat(info->t_dir1_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(info->t_dir1_fd, FILE2, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(info->t_dir1_fd, FILE2, 0))
+			die("failure: is_ixgrp");
+
+		/* create a character device via mknodat() vfs_mknod */
+		if (mknodat(info->t_dir1_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, makedev(5, 1)))
+			die("failure: mknodat");
+
+		if (is_setgid(info->t_dir1_fd, CHRDEV1, 0))
+			die("failure: is_setgid");
+
+		if (is_ixgrp(info->t_dir1_fd, CHRDEV1, 0))
+			die("failure: is_ixgrp");
+
+		/*
+		 * In setgid directories newly created files always inherit the
+		 * gid from the parent directory. Verify that the file is owned
+		 * by gid 0, not by gid 10000.
+		 */
+		if (!expected_uid_gid(info->t_dir1_fd, FILE1, 0, 0, 0))
+			die("failure: check ownership");
+
+		/*
+		 * In setgid directories newly created directories always
+		 * inherit the gid from the parent directory. Verify that the
+		 * directory is owned by gid 0, not by gid 10000.
+		 */
+		if (!expected_uid_gid(info->t_dir1_fd, DIR1, 0, 0, 0))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(info->t_dir1_fd, FILE2, 0, 0, 0))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(info->t_dir1_fd, CHRDEV1, 0, 0, 0))
+			die("failure: check ownership");
+
+		if (unlinkat(info->t_dir1_fd, FILE1, 0))
+			die("failure: delete");
+
+		if (unlinkat(info->t_dir1_fd, DIR1, AT_REMOVEDIR))
+			die("failure: delete");
+
+		if (unlinkat(info->t_dir1_fd, FILE2, 0))
+			die("failure: delete");
+
+		if (unlinkat(info->t_dir1_fd, CHRDEV1, 0))
+			die("failure: delete");
+
+		/* create tmpfile via filesystem tmpfile api */
+		if (supported) {
+			tmpfile_fd = openat(info->t_dir1_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
+			if (tmpfile_fd < 0)
+				die("failure: create");
+			/* link the temporary file into the filesystem, making it permanent */
+			if (linkat(tmpfile_fd, "", info->t_dir1_fd, FILE3, AT_EMPTY_PATH))
+				die("failure: linkat");
+			if (close(tmpfile_fd))
+				die("failure: close");
+			if (is_setgid(info->t_dir1_fd, FILE3, 0))
+				die("failure: is_setgid");
+			if (is_ixgrp(info->t_dir1_fd, FILE3, 0))
+				die("failure: is_ixgrp");
+			if (!expected_uid_gid(info->t_dir1_fd, FILE3, 0, 0, 0))
+				die("failure: check ownership");
+			if (unlinkat(info->t_dir1_fd, FILE3, 0))
+				die("failure: delete");
+		}
+
+		exit(EXIT_SUCCESS);
+	}
+	if (wait_for_pid(pid))
+		goto out;
+
+	pid = fork();
+	if (pid < 0) {
+		log_stderr("failure: fork");
+		goto out;
+	}
+	if (pid == 0) {
+		/* The group permissions correspond to the permissions of the
+		 * ACL_GROUP_OBJ entry.
+		 */
+		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
+		if (system(t_buf))
+			die("failure: system");
+
+		if (!switch_ids(0, 10000))
+			die("failure: switch_ids");
+
+		if (!caps_down_fsetid())
+			die("failure: caps_down_fsetid");
+
+		/* create regular file via open() */
+		file1_fd = openat(info->t_dir1_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
+		if (file1_fd < 0)
+			die("failure: create");
+
+		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
+		 * bit needs to be stripped.
+		 */
+		if (is_setgid(info->t_dir1_fd, FILE1, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(info->t_dir1_fd, FILE1, 0))
+			die("failure: is_ixgrp");
+
+		/* create directory */
+		if (mkdirat(info->t_dir1_fd, DIR1, 0000))
+			die("failure: create");
+
+		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
+			/* We're not in_group_p(). */
+			if (is_setgid(info->t_dir1_fd, DIR1, 0))
+				die("failure: is_setgid");
+		} else {
+			/* Directories always inherit the setgid bit. */
+			if (!is_setgid(info->t_dir1_fd, DIR1, 0))
+				die("failure: is_setgid");
+		}
+
+		if (is_ixgrp(info->t_dir1_fd, DIR1, 0))
+			die("failure: is_ixgrp");
+
+		/* create a special file via mknodat() vfs_create */
+		if (mknodat(info->t_dir1_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
+			die("failure: mknodat");
+
+		if (is_setgid(info->t_dir1_fd, FILE2, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(info->t_dir1_fd, FILE2, 0))
+			die("failure: is_ixgrp");
+
+		/* create a character device via mknodat() vfs_mknod */
+		if (mknodat(info->t_dir1_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, makedev(5, 1)))
+			die("failure: mknodat");
+
+		if (is_setgid(info->t_dir1_fd, CHRDEV1, 0))
+			die("failure: is_setgid");
+
+		if (!is_ixgrp(info->t_dir1_fd, CHRDEV1, 0))
+			die("failure: is_ixgrp");
+
+		/*
+		 * In setgid directories newly created files always inherit the
+		 * gid from the parent directory. Verify that the file is owned
+		 * by gid 0, not by gid 10000.
+		 */
+		if (!expected_uid_gid(info->t_dir1_fd, FILE1, 0, 0, 0))
+			die("failure: check ownership");
+
+		/*
+		 * In setgid directories newly created directories always
+		 * inherit the gid from the parent directory. Verify that the
+		 * directory is owned by gid 0, not by gid 10000.
+		 */
+		if (!expected_uid_gid(info->t_dir1_fd, DIR1, 0, 0, 0))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(info->t_dir1_fd, FILE2, 0, 0, 0))
+			die("failure: check ownership");
+
+		if (!expected_uid_gid(info->t_dir1_fd, CHRDEV1, 0, 0, 0))
+			die("failure: check ownership");
+
+		if (unlinkat(info->t_dir1_fd, FILE1, 0))
+			die("failure: delete");
+
+		if (unlinkat(info->t_dir1_fd, DIR1, AT_REMOVEDIR))
+			die("failure: delete");
+
+		if (unlinkat(info->t_dir1_fd, FILE2, 0))
+			die("failure: delete");
+
+		if (unlinkat(info->t_dir1_fd, CHRDEV1, 0))
+			die("failure: delete");
+
+		/* create tmpfile via filesystem tmpfile api */
+		if (supported) {
+			tmpfile_fd = openat(info->t_dir1_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
+			if (tmpfile_fd < 0)
+				die("failure: create");
+			/* link the temporary file into the filesystem, making it permanent */
+			if (linkat(tmpfile_fd, "", info->t_dir1_fd, FILE3, AT_EMPTY_PATH))
+				die("failure: linkat");
+			if (close(tmpfile_fd))
+				die("failure: close");
+			if (is_setgid(info->t_dir1_fd, FILE3, 0))
+				die("failure: is_setgid");
+			if (!is_ixgrp(info->t_dir1_fd, FILE3, 0))
+				die("failure: is_ixgrp");
+			if (!expected_uid_gid(info->t_dir1_fd, FILE3, 0, 0, 0))
+				die("failure: check ownership");
+			if (unlinkat(info->t_dir1_fd, FILE3, 0))
+				die("failure: delete");
+		}
+
+		exit(EXIT_SUCCESS);
+	}
+	if (wait_for_pid(pid))
+		goto out;
+
+	fret = 0;
+	log_debug("Ran test");
+out:
+	safe_close(file1_fd);
+
+	return fret;
+}
+
 static int setattr_truncate(const struct vfstest_info *info)
 {
 	int fret = -1;
@@ -1988,6 +2309,7 @@  static void usage(void)
 	fprintf(stderr, "--test-setattr-fix-968219708108     Run setattr regression tests\n");
 	fprintf(stderr, "--test-setxattr-fix-705191b03d50    Run setxattr regression tests\n");
 	fprintf(stderr, "--test-setgid-create-umask          Run setgid with umask tests\n");
+	fprintf(stderr, "--test-setgid-create-acl            Run setgid with acl tests\n");
 
 	_exit(EXIT_SUCCESS);
 }
@@ -2007,6 +2329,7 @@  static const struct option longopts[] = {
 	{"test-setattr-fix-968219708108",	no_argument,		0,	'i'},
 	{"test-setxattr-fix-705191b03d50",	no_argument,		0,	'j'},
 	{"test-setgid-create-umask",		no_argument,		0,	'u'},
+	{"test-setgid-create-acl",		no_argument,		0,	'l'},
 	{NULL,					0,			0,	  0},
 };
 
@@ -2041,6 +2364,15 @@  static const struct test_suite s_setgid_create_umask = {
 	.nr_tests = ARRAY_SIZE(t_setgid_create_umask),
 };
 
+static const struct test_struct t_setgid_create_acl[] = {
+	{ setgid_create_acl,						0,			"create operations in directories with setgid bit set under posix acl",				},
+};
+
+static const struct test_suite s_setgid_create_acl = {
+	.tests = t_setgid_create_acl,
+	.nr_tests = ARRAY_SIZE(t_setgid_create_acl),
+};
+
 static bool run_test(struct vfstest_info *info, const struct test_struct suite[], size_t suite_size)
 {
 	int i;
@@ -2139,7 +2471,7 @@  int main(int argc, char *argv[])
 	     test_core = false, test_fscaps_regression = false,
 	     test_nested_userns = false, test_setattr_fix_968219708108 = false,
 	     test_setxattr_fix_705191b03d50 = false,
-	     test_setgid_create_umask = false;
+	     test_setgid_create_umask = false, test_setgid_create_acl = false;
 
 	init_vfstest_info(&info);
 
@@ -2184,6 +2516,9 @@  int main(int argc, char *argv[])
 		case 'u':
 			test_setgid_create_umask = true;
 			break;
+		case 'l':
+			test_setgid_create_acl = true;
+			break;
 		case 'h':
 			/* fallthrough */
 		default:
@@ -2269,6 +2604,14 @@  int main(int argc, char *argv[])
 			goto out;
 	}
 
+	if (test_setgid_create_acl) {
+		if (!run_suite(&info, &s_setgid_create_acl))
+			goto out;
+
+		if (!run_suite(&info, &s_setgid_create_acl_idmapped_mounts))
+			goto out;
+	}
+
 	fret = EXIT_SUCCESS;
 
 out:
diff --git a/tests/generic/999 b/tests/generic/999
new file mode 100755
index 00000000..0c73e90e
--- /dev/null
+++ b/tests/generic/999
@@ -0,0 +1,33 @@ 
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 Fujitsu Limited. All Rights Reserved.
+#
+# FS QA Test No. 999
+#
+# Test S_ISGID stripping whether works correctly when call process
+# uses posix acl.
+#
+# It is also a regression test for
+# commit 1639a49ccdce ("fs: move S_ISGID stripping into the vfs_*() helpers")
+
+. ./common/preamble
+_begin_fstest auto quick cap acl idmapped mount perms rw unlink
+
+# Import common functions.
+. ./common/filter
+. ./common/attr
+
+# real QA test starts here
+
+_supported_fs generic
+_require_test
+_require_acls
+_fixed_by_kernel_commit 1639a49ccdce \
+	"fs: move S_ISGID stripping into the vfs_*() helpers"
+
+$here/src/vfs/vfstest --test-setgid-create-acl \
+        --device "$TEST_DEV" --mount "$TEST_DIR" --fstype "$FSTYP"
+
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/generic/999.out b/tests/generic/999.out
new file mode 100644
index 00000000..3b276ca8
--- /dev/null
+++ b/tests/generic/999.out
@@ -0,0 +1,2 @@ 
+QA output created by 999
+Silence is golden