From: Al Viro viro@zeniv.linux.org.uk
commit a0a6df9afcaf439a6b4c88a3b522e3d05fdef46f upstream.
Unfortunately, there's userland code that used to rely upon these checks being done before anything else to check for UMOUNT_NOFOLLOW support. That broke in 41525f56e256 ("fs: refactor ksys_umount"). Separate those from the rest of checks and move them to ksys_umount(); unlike everything else in there, this can be sanely done there.
Reported-by: Sargun Dhillon sargun@sargun.me Fixes: 41525f56e256 ("fs: refactor ksys_umount") Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/namespace.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/fs/namespace.c +++ b/fs/namespace.c @@ -1713,8 +1713,6 @@ static int can_umount(const struct path { struct mount *mnt = real_mount(path->mnt);
- if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) - return -EINVAL; if (!may_mount()) return -EPERM; if (path->dentry != path->mnt->mnt_root) @@ -1728,6 +1726,7 @@ static int can_umount(const struct path return 0; }
+// caller is responsible for flags being sane int path_umount(struct path *path, int flags) { struct mount *mnt = real_mount(path->mnt); @@ -1749,6 +1748,10 @@ static int ksys_umount(char __user *name struct path path; int ret;
+ // basic validity checks done first + if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) + return -EINVAL; + if (!(flags & UMOUNT_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);