linux-kernel - [ 158/171] libceph: avoid dropping con mutex before fault

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Message-Id: <20121122004049.212668349@linuxfoundation.org>
Date:	Wed, 21 Nov 2012 16:41:44 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Sage Weil <sage@...tank.com>,
	Alex Elder <elder@...tank.com>
Subject: [ 158/171] libceph: avoid dropping con mutex before fault

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sage Weil <sage@...tank.com>

(cherry picked from commit 8636ea672f0c5ab7478c42c5b6705ebd1db7eb6a)

The ceph_fault() function takes the con mutex, so we should avoid
dropping it before calling it.  This fixes a potential race with
another thread calling ceph_con_close(), or _open(), or similar (we
don't reverify con->state after retaking the lock).

Add annotation so that lockdep realizes we will drop the mutex before
returning.

Signed-off-by: Sage Weil <sage@...tank.com>
Reviewed-by: Alex Elder <elder@...tank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ceph/messenger.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2336,7 +2336,6 @@ done_unlocked:
 	return;
 
 fault:
-	mutex_unlock(&con->mutex);
 	ceph_fault(con);     /* error/fault path */
 	goto done_unlocked;
 }
@@ -2347,9 +2346,8 @@ fault:
  * exponential backoff
  */
 static void ceph_fault(struct ceph_connection *con)
+	__releases(con->mutex)
 {
-	mutex_lock(&con->mutex);
-
 	pr_err("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
 	       ceph_pr_addr(&con->peer_addr.in_addr), con->error_msg);
 	dout("fault %p state %lu to peer %s\n",


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