[PATCH 3.16 147/305] mnt: fs_fully_visible test the proper mount for MNT_LOCKED

[Ben Hutchings]

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

commit d71ed6c930ac7d8f88f3cef6624a7e826392d61f upstream.

MNT_LOCKED implies on a child mount implies the child is locked to the
parent.  So while looping through the children the children should be
tested (not their parent).

Typically an unshare of a mount namespace locks all mounts together
making both the parent and the slave as locked but there are a few
corner cases where other things work.

Fixes: ceeb0e5d39fc ("vfs: Ignore unlocked mounts in fs_fully_visible")
Reported-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3072,7 +3072,7 @@ static bool fs_fully_visible(struct file
 		list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
 			struct inode *inode = child->mnt_mountpoint->d_inode;
 			/* Only worry about locked mounts */
-			if (!(mnt->mnt.mnt_flags & MNT_LOCKED))
+			if (!(child->mnt.mnt_flags & MNT_LOCKED))
 				continue;
 			/* Is the directory permanetly empty? */
 			if (!is_empty_dir_inode(inode))