[ 3.5.y.z extended stable ] Patch "klist: del waiter from klist_remove_waiters before wakeup" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    klist: del waiter from klist_remove_waiters before wakeup

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 65ef645449f12bf858306d5c1e2b07e2c20233cf Mon Sep 17 00:00:00 2001
From: "wang, biao" <biao.wang at intel.com>
Date: Thu, 16 May 2013 09:50:13 +0800
Subject: [PATCH] klist: del waiter from klist_remove_waiters before wakeup
 waitting process

commit ac5a2962b02f57dea76d314ef2521a2170b28ab6 upstream.

There is a race between klist_remove and klist_release. klist_remove
uses a local var waiter saved on stack. When klist_release calls
wake_up_process(waiter->process) to wake up the waiter, waiter might run
immediately and reuse the stack. Then, klist_release calls
list_del(&waiter->list) to change previous
wait data and cause prior waiter thread corrupt.

The patch fixes it against kernel 3.9.

Signed-off-by: wang, biao <biao.wang at intel.com>
Acked-by: Peter Zijlstra <peterz at infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 lib/klist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/klist.c b/lib/klist.c
index 0874e41..358a368 100644
--- a/lib/klist.c
+++ b/lib/klist.c
@@ -193,10 +193,10 @@ static void klist_release(struct kref *kref)
 		if (waiter->node != n)
 			continue;

+		list_del(&waiter->list);
 		waiter->woken = 1;
 		mb();
 		wake_up_process(waiter->process);
-		list_del(&waiter->list);
 	}
 	spin_unlock(&klist_remove_lock);
 	knode_set_klist(n, NULL);
--
1.8.1.2