linux-kernel - [PATCH 4.0 045/220] staging: android: sync: Fix memory corruption in sync_timeline

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Message-Id: <20150502185856.319293129@linuxfoundation.org>
Date:	Sat,  2 May 2015 20:59:20 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Alistair Strachan <alistair.strachan@...tec.com>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Colin Cross <ccross@...gle.com>
Subject: [PATCH 4.0 045/220] staging: android: sync: Fix memory corruption in sync_timeline_signal().

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

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

From: Alistair Strachan <alistair.strachan@...tec.com>

commit 8e43c9c75faf2902955bd2ecd7a50a8cc41cb00a upstream.

The android_fence_release() function checks for active sync points
by calling list_empty() on the list head embedded on the sync
point. However, it is only valid to use list_empty() on nodes that
have been initialized with INIT_LIST_HEAD() or list_del_init().

Because the list entry has likely been removed from the active list
by sync_timeline_signal(), there is a good chance that this
WARN_ON_ONCE() will be hit due to dangling pointers pointing at
freed memory (even though the sync drivers did nothing wrong)
and memory corruption will ensue as the list entry is removed for
a second time, corrupting the active list.

This problem can be reproduced quite easily with CONFIG_DEBUG_LIST=y
and fences with more than one sync point.

Signed-off-by: Alistair Strachan <alistair.strachan@...tec.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...onical.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Colin Cross <ccross@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/android/sync.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/android/sync.c
+++ b/drivers/staging/android/sync.c
@@ -114,7 +114,7 @@ void sync_timeline_signal(struct sync_ti
 	list_for_each_entry_safe(pt, next, &obj->active_list_head,
 				 active_list) {
 		if (fence_is_signaled_locked(&pt->base))
-			list_del(&pt->active_list);
+			list_del_init(&pt->active_list);
 	}

 	spin_unlock_irqrestore(&obj->child_list_lock, flags);

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