| From 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 Mon Sep 17 00:00:00 2001 |
| From: Al Viro <viro@zeniv.linux.org.uk> |
| Date: Fri, 24 Apr 2015 15:47:07 -0400 |
| Subject: RCU pathwalk breakage when running into a symlink overmounting something |
| |
| From: Al Viro <viro@zeniv.linux.org.uk> |
| |
| 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(). |
| |
| Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/namei.c | 6 ++++-- |
| 1 file changed, 4 insertions(+), 2 deletions(-) |
| |
| --- a/fs/namei.c |
| +++ b/fs/namei.c |
| @@ -1591,7 +1591,8 @@ static inline int walk_component(struct |
| |
| if (should_follow_link(path->dentry, follow)) { |
| if (nd->flags & LOOKUP_RCU) { |
| - if (unlikely(unlazy_walk(nd, path->dentry))) { |
| + if (unlikely(nd->path.mnt != path->mnt || |
| + unlazy_walk(nd, path->dentry))) { |
| err = -ECHILD; |
| goto out_err; |
| } |
| @@ -3047,7 +3048,8 @@ finish_lookup: |
| |
| if (should_follow_link(path->dentry, !symlink_ok)) { |
| if (nd->flags & LOOKUP_RCU) { |
| - if (unlikely(unlazy_walk(nd, path->dentry))) { |
| + if (unlikely(nd->path.mnt != path->mnt || |
| + unlazy_walk(nd, path->dentry))) { |
| error = -ECHILD; |
| goto out; |
| } |
