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| author | Al Viro <viro@zeniv.linux.org.uk> | 2015-04-24 15:47:07 -0400 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-05-17 19:12:25 -0400 |
| commit | c5f77349d6694a2ce04536343fee87a0de74522d (patch) | |
| tree | 3c5c56fa1ddcc9d73868dbde59e622df85a8e9cc /fs/namei.c | |
| parent | 3d46720fc10e8270d003fa8e55f2e89c14af9261 (diff) | |
| download | lwn-c5f77349d6694a2ce04536343fee87a0de74522d.tar.gz lwn-c5f77349d6694a2ce04536343fee87a0de74522d.zip | |
RCU pathwalk breakage when running into a symlink overmounting something
[ Upstream commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 ]
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().
Cc: stable@vger.kernel.org # since 2.6.39
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c index db5fe86319e6..890d3580bf0e 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1560,7 +1560,8 @@ static inline int walk_component(struct nameidata *nd, struct path *path, 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; } @@ -3015,7 +3016,8 @@ 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; } |