From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
[ 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@xxxxxxxxxxxxxxx # since 2.6.39
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
fs/namei.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index db5fe86..890d358 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;
}
--
2.1.0
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