decode: be more explicit about storing the last packet properties

The current code stores a pointer to the packet passed to the decoder,
which is then used during get_buffer() for timestamps and side data
passthrough. However, since this is a pointer to user data which we do
not own, storing it is potentially dangerous. It is also ill defined for
the new decoding API with split input/output.

Fix this problem by making an explicit internally owned copy of the
packet properties.

1 files changed, 8 insertions, 0 deletions

diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 5350eb819a..b569b48f7a 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -433,6 +433,12 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *code
         goto free_and_end;
     }
 
+    avctx->internal->last_pkt_props = av_packet_alloc();
+    if (!avctx->internal->last_pkt_props) {
+        ret = AVERROR(ENOMEM);
+        goto free_and_end;
+    }
+
     if (codec->priv_data_size > 0) {
         if (!avctx->priv_data) {
             avctx->priv_data = av_mallocz(codec->priv_data_size);
@@ -713,6 +719,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         av_frame_free(&avctx->internal->to_free);
         av_frame_free(&avctx->internal->buffer_frame);
         av_packet_free(&avctx->internal->buffer_pkt);
+        av_packet_free(&avctx->internal->last_pkt_props);
         av_freep(&avctx->internal->pool);
     }
     av_freep(&avctx->internal);
@@ -753,6 +760,7 @@ av_cold int avcodec_close(AVCodecContext *avctx)
         av_frame_free(&avctx->internal->to_free);
         av_frame_free(&avctx->internal->buffer_frame);
         av_packet_free(&avctx->internal->buffer_pkt);
+        av_packet_free(&avctx->internal->last_pkt_props);
         for (i = 0; i < FF_ARRAY_ELEMS(pool->pools); i++)
             av_buffer_pool_uninit(&pool->pools[i]);
         av_freep(&avctx->internal->pool);