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authorAl Viro <viro@zeniv.linux.org.uk>2021-01-04 15:25:34 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2021-01-04 15:31:58 -0500
commita0a6df9afcaf439a6b4c88a3b522e3d05fdef46f (patch)
tree7ef2ed36a935d9643b6e6b50988054a603187755 /fs/namespace.c
parent5c8fe583cce542aa0b84adc939ce85293de36e5e (diff)
umount(2): move the flag validity checks first
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>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index d2db7dfe232b..9d33909d0f9e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1713,8 +1713,6 @@ static int can_umount(const struct path *path, int flags)
{
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 *path, int flags)
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, int flags)
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);