linux-kernel - [PATCH 1/3] autofs4 - fix get_next_positive

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Date:	Tue, 18 Jan 2011 12:06:04 +0800
From:	Ian Kent <raven@...maw.net>
To:	Nick Piggin <npiggin@...e.de>, David Howells <dhowells@...hat.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 1/3] autofs4 - fix get_next_positive_dentry()

The initialization condition in fs/autofs4/expire.c:get_next_positive_dentry()
appears to be incorrect. If prev == NULL I believe that root should be
returned.

Further down, at the current dentry check for it being simple_positive()
it looks like the d_lock for dentry p should be dropped instead of dentry
ret, otherwise when p is assinged to ret we end up with no lock on p and
a lost lock on ret, which leads to a deadlock.
---

 fs/autofs4/expire.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 3ed79d7..f43100b 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -96,7 +96,7 @@ static struct dentry *get_next_positive_dentry(struct dentry *prev,
 	struct dentry *p, *ret;
 
 	if (prev == NULL)
-		return dget(prev);
+		return dget(root);
 
 	spin_lock(&autofs4_lock);
 relock:
@@ -133,7 +133,7 @@ again:
 	spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 	/* Negative dentry - try next */
 	if (!simple_positive(ret)) {
-		spin_unlock(&ret->d_lock);
+		spin_unlock(&p->d_lock);
 		p = ret;
 		goto again;
 	}

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