Prevents using GetBitContexts with data from previous calls.

Fixes access to freed memory.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC:[email protected]
---
 libavcodec/h264.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index d43b11e..adb0dbe 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -4750,6 +4750,13 @@ again:
                 }
                 break;
             case NAL_DPA:
+                if (h->avctx->flags & CODEC_FLAG2_CHUNKS) {
+                    av_log(h->avctx, AV_LOG_ERROR,
+                           "Decoding in chunks is not supported for "
+                           "partitioned slices.\n");
+                    return AVERROR(ENOSYS);
+                }
+
                 init_get_bits(&hx->gb, ptr, bit_length);
                 hx->intra_gb_ptr =
                 hx->inter_gb_ptr = NULL;
@@ -4899,6 +4906,9 @@ static int h264_decode_frame(AVCodecContext *avctx, void 
*data,
     int ret;
 
     h->flags = avctx->flags;
+    /* reset data partitioning here, to ensure GetBitContexts from previous
+     * packets do not get used. */
+    h->data_partitioning = 0;
 
     /* end of stream, output what is still in the buffers */
 out:
-- 
1.7.10.4

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