[PATCH] klist: del waiter from klist_remove_waiters before wakeup waitting process

[wangbiao <biao.wang@intel.com>]

From: "wang, biao" <biao.wang@intel.com>
Date: Fri, 3 May 2013 14:18:34 +0800
Subject: [PATCH] klist: del waiter from klist_remove_waiters before wakeup
 waitting process

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@intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
---
 lib/klist.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

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);
-- 
1.7.6