RCU pathwalk breakage when running into a symlink overmounting something
commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 upstream.
Calling unlazy_walk() in walk_component() and do_last() when we find
a symlink that needs to be followed doesn't acquire a reference to vfsmount.
That's fine when the symlink is on the same vfsmount as the parent directory
(which is almost always the case), but it's not always true - one _can_
manage to bind a symlink on top of something. And in such cases we end up
with excessive mntput().
Change-Id: I699ac270e81cb22e90f9974c4189965745e708f5
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[lizf: Backported to 3.4: drop the changes to do_last()]
Signed-off-by: Zefan Li <lizefan@huawei.com>
1 file changed