From: Al Viro <viro@zeniv.linux.org.uk>
Date: Wed, 13 Jul 2011 01:40:23 +0000 (-0400)
Subject: Fix ->d_lock locking order in unlazy_walk()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=94c0d4ecbe7f9fe56e052b26b2ab484e246c07b4;p=linux-beck.git

Fix ->d_lock locking order in unlazy_walk()

Make sure that child is still a child of parent before nested locking
of child->d_lock in unlazy_walk(); otherwise we are risking a violation
of locking order and deadlocks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/namei.c b/fs/namei.c
index 0223c41fb114..5c867dd1c0b3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -433,6 +433,8 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
 			goto err_parent;
 		BUG_ON(nd->inode != parent->d_inode);
 	} else {
+		if (dentry->d_parent != parent)
+			goto err_parent;
 		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 		if (!__d_rcu_to_refcount(dentry, nd->seq))
 			goto err_child;