From: wang, biao <biao.wang@intel.com>
Date: Thu, 16 May 2013 01:50:13 +0000 (+0800)
Subject: klist: del waiter from klist_remove_waiters before wakeup waitting process
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=ac5a2962b02f57dea76d314ef2521a2170b28ab6;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/lib/klist.c b/lib/klist.c
index 0874e41609a6..358a368a2947 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);