This is a note to let you know that I've just added the patch titled
RCU pathwalk breakage when running into a symlink overmounting something
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rcu-pathwalk-breakage-when-running-into-a-symlink-overmounting-something.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Fri, 24 Apr 2015 15:47:07 -0400
Subject: RCU pathwalk breakage when running into a symlink overmounting something
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/namei.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1585,7 +1585,8 @@ static inline int walk_component(struct
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;
}
@@ -3028,7 +3029,8 @@ 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;
}
Patches currently in stable-queue which might be from viro@xxxxxxxxxxxxxxxxxx are
queue-3.19/fs-binfmt_elf.c-fix-bug-in-loading-of-pie-binaries.patch
queue-3.19/rcu-pathwalk-breakage-when-running-into-a-symlink-overmounting-something.patch
queue-3.19/nfs-fix-bug-crash-in-notify_change-with-patch-to-chown_common.patch
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