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| author | Al Viro <viro@zeniv.linux.org.uk> | 2015-04-24 22:47:07 +0300 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2015-04-24 22:52:14 +0300 |
| commit | 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 (patch) | |
| tree | c696367810e2e603c3156127b6fb0eb4627a7132 | |
| parent | ac74d8d65c83d8061034d0908e1eab6a0c24f923 (diff) | |
| download | linux-3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647.tar.xz | |
RCU pathwalk breakage when running into a symlink overmounting something
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>
| -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 ffab2e06e147..4a8d998b7274 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1590,7 +1590,8 @@ 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; } @@ -3045,7 +3046,8 @@ 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; } |