[5/9] Implement fsmount() to effect a pre-configured mount

Message ID	149382751575.30481.5197100856310494934.stgit@warthog.procyon.org.uk (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-nfs-owner@kernel.org> DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com C0671448D95 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 5/9] Implement fsmount() to effect a pre-configured mount From: David Howells <dhowells@redhat.com> To: viro@zeniv.linux.org.uk Cc: linux-fsdevel@vger.kernel.org, dhowells@redhat.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, mszeredi@redhat.com Date: Wed, 03 May 2017 17:05:15 +0100 Message-ID: <149382751575.30481.5197100856310494934.stgit@warthog.procyon.org.uk> In-Reply-To: <149382747487.30481.15428192741961545429.stgit@warthog.procyon.org.uk> References: <149382747487.30481.15428192741961545429.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 9bf8d4c62f85..abe6ea95e0e6 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -392,3 +392,4 @@ 383 i386 statx sys_statx 384 i386 arch_prctl sys_arch_prctl compat_sys_arch_prctl 385 i386 fsopen sys_fsopen +386 i386 fsmount sys_fsmount diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 9b198c5fc412..0977c5079831 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -340,6 +340,7 @@ 331 common pkey_free sys_pkey_free 332 common statx sys_statx 333 common fsopen sys_fsopen +334 common fsmount sys_fsmount # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/fs/namespace.c b/fs/namespace.c index e0edab9af308..a367b6cb2ac8 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3259,6 +3259,99 @@ static int do_new_mount_mc(struct mount_context *mc, struct path *mountpoint, } /* + * Mount a new, prepared superblock (specified by fs_fd) on the location + * specified by dfd and dir_name. dfd can be AT_FDCWD, a dir fd or a container + * fd. This cannot be used for binding, moving or remounting mounts. + * + * If fd is a container and dir_name is NULL, then we try to make this the root + * filesystem of that container. This requires CONTAINER_NEW_EMPTY_FS_NS to + * have been passed when creating the container. This operation may only be + * done once. + */ +SYSCALL_DEFINE3(fsmount, int, fs_fd, int, dfd, const char __user *, dir_name) +{ + struct mount_context *mc; + struct inode *inode; + struct path mountpoint; + struct fd f = fdget(fs_fd); + unsigned int mnt_flags = 0; + long ret; + + if (!f.file) + return -EBADF; + + ret = -EINVAL; + if (f.file->f_op != &fs_fs_fops) + goto err_fsfd; + + mc = f.file->private_data; + + ret = -EPERM; + if (!may_mount() || + ((mc->ms_flags & MS_MANDLOCK) && !may_mandlock())) + goto err_fsfd; + + /* Prevent further changes. */ + inode = file_inode(f.file); + ret = inode_lock_killable(inode); + if (ret < 0) + goto err_fsfd; + ret = -EBUSY; + if (!mc->mounted) { + mc->mounted = true; + ret = 0; + } + inode_unlock(inode); + if (ret < 0) + goto err_fsfd; + + /* Find the mountpoint. A container can be specified in dfd. */ + ret = user_path_at(dfd, dir_name, LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, + &mountpoint); + if (ret < 0) { + mc->error = "VFS: Mountpoint lookup failed"; + goto err_fsfd; + } + + ret = security_mount_ctx_mountpoint(mc, &mountpoint); + if (ret < 0) + goto err_mp; + + /* Default to relatime unless overriden */ + if (!(mc->ms_flags & MS_NOATIME)) + mnt_flags |= MNT_RELATIME; + + /* Separate the per-mountpoint flags */ + if (mc->ms_flags & MS_NOSUID) + mnt_flags |= MNT_NOSUID; + if (mc->ms_flags & MS_NODEV) + mnt_flags |= MNT_NODEV; + if (mc->ms_flags & MS_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (mc->ms_flags & MS_NOATIME) + mnt_flags |= MNT_NOATIME; + if (mc->ms_flags & MS_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + if (mc->ms_flags & MS_STRICTATIME) + mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); + if (mc->ms_flags & MS_RDONLY) + mnt_flags |= MNT_READONLY; + mc->mnt_flags = mnt_flags; + + mc->ms_flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | + MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | + MS_STRICTATIME | MS_NOREMOTELOCK | MS_SUBMOUNT); + + ret = do_new_mount_mc(mc, &mountpoint, mnt_flags); + +err_mp: + path_put(&mountpoint); +err_fsfd: + fdput(f); + return ret; +} + +/* * Return true if path is reachable from root * * namespace_sem or mount_lock is held diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index f6aa68b8e68e..fe2bffd7264d 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -100,6 +100,10 @@ * Equivalent of sb_kern_mount, but with a mount_context. * @mc indicates the mount context. * @src_sb indicates the new superblock. + * @mount_ctx_mountpoint: + * Equivalent of sb_mount, but with a mount_context. + * @mc indicates the mount context. + * @mountpoint indicates the path on which the mount will take place. * * Security hooks for filesystem operations. * @@ -1389,6 +1393,7 @@ union security_list_options { void (*mount_ctx_free)(struct mount_context *mc); int (*mount_ctx_option)(struct mount_context *mc, char *opt); int (*mount_ctx_kern_mount)(struct mount_context *mc, struct super_block *sb); + int (*mount_ctx_mountpoint)(struct mount_context *mc, struct path *mountpoint); int (*sb_alloc_security)(struct super_block *sb); void (*sb_free_security)(struct super_block *sb); @@ -1703,6 +1708,7 @@ struct security_hook_heads { struct list_head mount_ctx_free; struct list_head mount_ctx_option; struct list_head mount_ctx_kern_mount; + struct list_head mount_ctx_mountpoint; struct list_head sb_alloc_security; struct list_head sb_free_security; struct list_head sb_copy_data; diff --git a/include/linux/security.h b/include/linux/security.h index 91efe3039bff..b427a554033a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -226,6 +226,7 @@ int security_mount_ctx_dup(struct mount_context *mc, struct mount_context *src); void security_mount_ctx_free(struct mount_context *mc); int security_mount_ctx_option(struct mount_context *mc, char *opt); int security_mount_ctx_kern_mount(struct mount_context *mc, struct super_block *sb); +int security_mount_ctx_mountpoint(struct mount_context *mc, struct path *mountpoint); int security_sb_alloc(struct super_block *sb); void security_sb_free(struct super_block *sb); int security_sb_copy_data(char *orig, char *copy); @@ -541,6 +542,11 @@ static inline int security_mount_ctx_kern_mount(struct mount_context *mc, { return 0; } +static inline int security_mount_ctx_mountpoint(struct mount_context *mc, + struct path *mountpoint) +{ + return 0; +} static inline int security_sb_alloc(struct super_block *sb) { diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 91ec8802ad5d..9ac7d8ca8c2e 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -906,5 +906,6 @@ asmlinkage long sys_pkey_free(int pkey); asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, unsigned mask, struct statx __user *buffer); asmlinkage long sys_fsopen(const char *fs_name, int containerfd, unsigned int flags); +asmlinkage long sys_fsmount(int fsfd, int dfd, const char *path); #endif diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index de1dc63e7e47..a0fe764bd5dd 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -261,3 +261,4 @@ cond_syscall(sys_pkey_free); /* fd-based mount */ cond_syscall(sys_fsopen); +cond_syscall(sys_fsmount); diff --git a/security/security.c b/security/security.c index 2e522361df66..56780c1852b5 100644 --- a/security/security.c +++ b/security/security.c @@ -334,6 +334,11 @@ int security_mount_ctx_kern_mount(struct mount_context *mc, struct super_block * return call_int_hook(mount_ctx_kern_mount, 0, mc, sb); } +int security_mount_ctx_mountpoint(struct mount_context *mc, struct path *mountpoint) +{ + return call_int_hook(mount_ctx_mountpoint, 0, mc, mountpoint); +} + int security_sb_alloc(struct super_block *sb) { return call_int_hook(sb_alloc_security, 0, sb); @@ -1691,6 +1696,8 @@ struct security_hook_heads security_hook_heads = { LIST_HEAD_INIT(security_hook_heads.mount_ctx_option), .mount_ctx_kern_mount = LIST_HEAD_INIT(security_hook_heads.mount_ctx_kern_mount), + .mount_ctx_mountpoint = + LIST_HEAD_INIT(security_hook_heads.mount_ctx_mountpoint), .sb_alloc_security = LIST_HEAD_INIT(security_hook_heads.sb_alloc_security), .sb_free_security = diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index cf38db840f71..2bd8e73eb9c9 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2999,6 +2999,18 @@ static int selinux_mount_ctx_kern_mount(struct mount_context *mc, return rc; } +static int selinux_mount_ctx_mountpoint(struct mount_context *mc, + struct path *mountpoint) +{ + const struct cred *cred = current_cred(); + int ret; + + ret = path_has_perm(cred, mountpoint, FILE__MOUNTON); + if (ret < 0) + mc->error = "SELinux: Mount on mountpoint not permitted"; + return ret; +} + /* inode security operations */ static int selinux_inode_alloc_security(struct inode *inode) @@ -6309,6 +6321,7 @@ static struct security_hook_list selinux_hooks[] = { LSM_HOOK_INIT(mount_ctx_free, selinux_mount_ctx_free), LSM_HOOK_INIT(mount_ctx_option, selinux_mount_ctx_option), LSM_HOOK_INIT(mount_ctx_kern_mount, selinux_mount_ctx_kern_mount), + LSM_HOOK_INIT(mount_ctx_mountpoint, selinux_mount_ctx_mountpoint), LSM_HOOK_INIT(sb_alloc_security, selinux_sb_alloc_security), LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security),

[5/9] Implement fsmount() to effect a pre-configured mount

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