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authorAl Viro <viro@zeniv.linux.org.uk>2015-04-24 15:47:07 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2015-04-24 15:52:14 -0400
commit3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 (patch)
treec696367810e2e603c3156127b6fb0eb4627a7132
parentac74d8d65c83d8061034d0908e1eab6a0c24f923 (diff)
downloadlinux-stericsson-3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647.tar.gz
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.c6
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;
}