[FFmpeg-cvslog] Check for overread in vqa video decoder.

[Reimar Döffinger]

ffmpeg | branch: master | Reimar Döffinger <Reimar.Doeffinger at gmx.de> | Thu Jan  5 18:25:40 2012 +0100| [427802324098eff19b307b486179b56d8b50b9a8] | committer: Reimar Döffinger

Check for overread in vqa video decoder.

This issue was discovered while decoding the FATE sample vqa/ws_snd.vqa.
For some unknown reason only audio decoding is tested by FATE for that file,
but not video.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=427802324098eff19b307b486179b56d8b50b9a8
---

 libavcodec/vqavideo.c |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/libavcodec/vqavideo.c b/libavcodec/vqavideo.c
index 917e04b..ae99c6d 100644
--- a/libavcodec/vqavideo.c
+++ b/libavcodec/vqavideo.c
@@ -322,10 +322,17 @@ static void vqa_decode_chunk(VqaContext *s)
     int hibytes = s->decode_buffer_size / 2;
 
     /* first, traverse through the frame and find the subchunks */
-    while (index < s->size) {
+    while (index + CHUNK_PREAMBLE_SIZE <= s->size) {
+        unsigned next_index;
 
         chunk_type = AV_RB32(&s->buf[index]);
         chunk_size = AV_RB32(&s->buf[index + 4]);
+        byte_skip = chunk_size & 0x01;
+        next_index = index + CHUNK_PREAMBLE_SIZE + chunk_size + byte_skip;
+        if (next_index > s->size) {
+            av_log(s->avctx, AV_LOG_ERROR, "Dropping incomplete chunk\n");
+            break;
+        }
 
         switch (chunk_type) {
 
@@ -366,9 +373,7 @@ static void vqa_decode_chunk(VqaContext *s)
             chunk_type);
             break;
         }
-
-        byte_skip = chunk_size & 0x01;
-        index += (CHUNK_PREAMBLE_SIZE + chunk_size + byte_skip);
+        index = next_index;
     }
 
     /* next, deal with the palette */