linux-kernel - [ 21/44] klist: del waiter from klist_remove

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Message-Id: <20130605211224.082345886@linuxfoundation.org>
Date:	Wed,  5 Jun 2013 14:12:19 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, "wang, biao" <biao.wang@...el.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [ 21/44] klist: del waiter from klist_remove_waiters before wakeup waitting process

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

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

From: "wang, biao" <biao.wang@...el.com>

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@...el.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 lib/klist.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/klist.c
+++ b/lib/klist.c
@@ -193,10 +193,10 @@ static void klist_release(struct kref *k
 		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);


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