h264: stricter reference limit enforcement.

Message ID 20120314202813.045825E0DC@aruru.libav.org
State New
Headers show

Commit Message

Janne Grunau March 14, 2012, 8:28 p.m.
Module: libav
Branch: master
Commit: e0febda22d0e0fab094a9c886b0e0f0f662df1ef

Author:    Ronald S. Bultje <rsbultje@gmail.com>
Committer: Ronald S. Bultje <rsbultje@gmail.com>
Date:      Tue Mar 13 16:26:44 2012 -0700

h264: stricter reference limit enforcement.

Progressive images can have only 16 references, error out if there are
more, since the data is almost certainly corrupt, and the invalid value
will lead to random crashes or invalid writes later on.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

---

 libavcodec/h264.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

Patch

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index c3ef3f0..64f676c 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -3021,6 +3021,8 @@  static int decode_slice_header(H264Context *h, H264Context *h0){
     h->ref_count[1]= h->pps.ref_count[1];
 
     if(h->slice_type_nos != AV_PICTURE_TYPE_I){
+        int max_refs = s->picture_structure == PICT_FRAME ? 16 : 32;
+
         if(h->slice_type_nos == AV_PICTURE_TYPE_B){
             h->direct_spatial_mv_pred= get_bits1(&s->gb);
         }
@@ -3030,13 +3032,14 @@  static int decode_slice_header(H264Context *h, H264Context *h0){
             h->ref_count[0]= get_ue_golomb(&s->gb) + 1;
             if(h->slice_type_nos==AV_PICTURE_TYPE_B)
                 h->ref_count[1]= get_ue_golomb(&s->gb) + 1;
+        }
 
-            if(h->ref_count[0]-1 > 32-1 || h->ref_count[1]-1 > 32-1){
-                av_log(h->s.avctx, AV_LOG_ERROR, "reference overflow\n");
-                h->ref_count[0]= h->ref_count[1]= 1;
-                return -1;
-            }
+        if (h->ref_count[0] > max_refs || h->ref_count[1] > max_refs) {
+            av_log(h->s.avctx, AV_LOG_ERROR, "reference overflow\n");
+            h->ref_count[0] = h->ref_count[1] = 1;
+            return AVERROR_INVALIDDATA;
         }
+
         if(h->slice_type_nos == AV_PICTURE_TYPE_B)
             h->list_count= 2;
         else