mpeg12: do not decode extradata more than once.

Fixes CVE-2012-2803.

CC: libav-stable@libav.org

diff --git a/libavcodec/mpeg12.c b/libavcodec/mpeg12.c
index 83069f5..7a9b54a 100644 (file)
--- a/libavcodec/mpeg12.c
+++ b/libavcodec/mpeg12.c
@@ -2456,8 +2456,9 @@ static int mpeg_decode_frame(AVCodecContext *avctx,
 
     s->slice_count = 0;
 
-    if (avctx->extradata && !avctx->frame_number) {
+    if (avctx->extradata && !s->extradata_decoded) {
         int ret = decode_chunks(avctx, picture, got_output, avctx->extradata, avctx->extradata_size);
+        s->extradata_decoded = 1;
         if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE))
             return ret;
     }

diff --git a/libavcodec/mpeg12.h b/libavcodec/mpeg12.h
index ab0352f..0f9faaf 100644 (file)
--- a/libavcodec/mpeg12.h
+++ b/libavcodec/mpeg12.h
@@ -42,6 +42,7 @@ typedef struct Mpeg1Context {
     AVRational frame_rate_ext;       ///< MPEG-2 specific framerate modificator
     int sync;                        ///< Did we reach a sync point like a GOP/SEQ/KEYFrame?
     int closed_gop;                  ///< GOP is closed
+    int extradata_decoded;
 } Mpeg1Context;
 
 extern uint8_t ff_mpeg12_static_rl_table_store[2][2][2*MAX_RUN + MAX_LEVEL + 3];