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| author | Al Viro <viro@zeniv.linux.org.uk> | 2015-04-24 15:47:07 -0400 |
|---|---|---|
| committer | Zefan Li <lizefan@huawei.com> | 2015-09-18 09:20:32 +0800 |
| commit | a26f33c50cb736da55437cef761d48d72fe89d3e (patch) | |
| tree | 51d8d79937c6c8c3ab10511867f7d72a424cf490 | |
| parent | 20db578815361ac06fca1c03ef555324f00111d0 (diff) | |
| download | lwn-a26f33c50cb736da55437cef761d48d72fe89d3e.tar.gz lwn-a26f33c50cb736da55437cef761d48d72fe89d3e.zip | |
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().
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>
| -rw-r--r-- | fs/namei.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/namei.c b/fs/namei.c index bdcd70544fce..9c4b9b811d7b 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1314,7 +1314,8 @@ static inline int walk_component(struct nameidata *nd, struct path *path, } if (should_follow_link(inode, 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))) { terminate_walk(nd); return -ECHILD; } |