[v6,21/40] ioctl: handle idmapped mounts

Commit Message

Christian Brauner Jan. 21, 2021, 1:19 p.m. UTC

Enable generic ioctls to handle idmapped mounts by passing down the
mount's user namespace. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/[e-mail]
Cc: Christoph Hellwig <[e-mail]>
Cc: David Howells <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: [e-mail]
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>
---
/* v2 */
patch introduced

/* v3 */
unchanged

/* v4 */
- Serge Hallyn <[e-mail]>:
  - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make
    terminology consistent.

/* v5 */
unchanged
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837

- Christoph Hellwig <[e-mail]>:
  - Use new file_mnt_user_ns() helper.

/* v6 */
base-commit: 19c329f6808995b142b3966301f217c831e7cf31

- Christoph Hellwig <[e-mail]>:
  - Make use of file_permission() helper.
---
 fs/remap_range.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Comments

James Morris Jan. 22, 2021, 4:33 a.m. UTC | #1

On Thu, 21 Jan 2021, Christian Brauner wrote:

> Enable generic ioctls to handle idmapped mounts by passing down the
> mount's user namespace. If the initial user namespace is passed nothing
> changes so non-idmapped mounts will see identical behavior as before.
> 
> Link: https://lore.kernel.org/r/[e-mail]
> Cc: Christoph Hellwig <[e-mail]>
> Cc: David Howells <[e-mail]>
> Cc: Al Viro <[e-mail]>
> Cc: [e-mail]
> Reviewed-by: Christoph Hellwig <[e-mail]>
> Signed-off-by: Christian Brauner <[e-mail]>


Reviewed-by: James Morris <[e-mail]>

Patch

diff --git a/fs/remap_range.c b/fs/remap_range.c
index 29a4a4dbfe12..e4a5fdd7ad7b 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -432,13 +432,16 @@  EXPORT_SYMBOL(vfs_clone_file_range);
 /* Check whether we are allowed to dedupe the destination file */
 static bool allow_file_dedupe(struct file *file)
 {
+	struct user_namespace *mnt_userns = file_mnt_user_ns(file);
+	struct inode *inode = file_inode(file);
+
 	if (capable(CAP_SYS_ADMIN))
 		return true;
 	if (file->f_mode & FMODE_WRITE)
 		return true;
-	if (uid_eq(current_fsuid(), file_inode(file)->i_uid))
+	if (uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode)))
 		return true;
-	if (!inode_permission(&init_user_ns, file_inode(file), MAY_WRITE))
+	if (!inode_permission(mnt_userns, inode, MAY_WRITE))
 		return true;
 	return false;
 }