[SCM] libav/wheezy-security: vp8: avoid race condition on segment map.

[siretart at users.alioth.debian.org]

The following commit has been merged in the wheezy-security branch:
commit 57c36de7265761dd94fb6bb4a9180011f796128f
Author: Aaron Colwell <acolwell at chromium.org>
Date:   Sun Mar 18 20:03:00 2012 -0700

    vp8: avoid race condition on segment map.
    
    This change avoids accessing the segment map of the previous frame if
    segmentation is not enabled for the current frame. The caller of
    decode_mb_mode() only calls ff_thread_await_progress() on the reference
    segmentation index array if segmentation is enabled, so Chromium's TSAN
    will report a race when accessing this data while segmentation is not
    enabled.
    
    Signed-off-by: Ronald S. Bultje <rsbultje at gmail.com>
    (cherry picked from commit 30011bf20109eef1a0f9ee949b19f9998ad88663)
    Signed-off-by: Diego Biurrun <diego at biurrun.de>

diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
index a16f5ca..0b6d818 100644
--- a/libavcodec/vp8.c
+++ b/libavcodec/vp8.c
@@ -642,7 +642,7 @@ void decode_mb_mode(VP8Context *s, VP8Macroblock *mb, int mb_x, int mb_y, uint8_
 
     if (s->segmentation.update_map)
         *segment = vp8_rac_get_tree(c, vp8_segmentid_tree, s->prob->segmentid);
-    else
+    else if (s->segmentation.enabled)
         *segment = ref ? *ref : *segment;
     s->segment = *segment;
 

-- 
Libav/FFmpeg packaging