avcodec/nvdec: don't free NVDECContext->bitstream

Ensure all hwaccels that allocate a buffer use NVDECContext->bitstream_internal
instead. Otherwise, if FFHWAccel->end_frame() isn't called before
FFHWAccel->uninit(), an attempt to free a stale pointer to memory not owned by
the hwaccel could take place.

Reviewed-by: Timo Rothenpieler <timo@rothenpieler.org>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/nvdec.c

@@ -258,8 +258,8 @@ int ff_nvdec_decode_uninit(AVCodecContext *avctx)
 {
     NVDECContext *ctx = avctx->internal->hwaccel_priv_data;
 
-    av_freep(&ctx->bitstream);
     av_freep(&ctx->bitstream_internal);
+    ctx->bitstream           = NULL;
     ctx->bitstream_len       = 0;
     ctx->bitstream_allocated = 0;
 

libavcodec/nvdec_h264.c

@@ -138,11 +138,11 @@ static int nvdec_h264_decode_slice(AVCodecContext *avctx, const uint8_t *buffer,
     const H264SliceContext *sl = &h->slice_ctx[0];
     void *tmp;
 
-    tmp = av_fast_realloc(ctx->bitstream, &ctx->bitstream_allocated,
+    tmp = av_fast_realloc(ctx->bitstream_internal, &ctx->bitstream_allocated,
                           ctx->bitstream_len + size + 3);
     if (!tmp)
         return AVERROR(ENOMEM);
-    ctx->bitstream = tmp;
+    ctx->bitstream = ctx->bitstream_internal = tmp;
 
     tmp = av_fast_realloc(ctx->slice_offsets, &ctx->slice_offsets_allocated,
                           (ctx->nb_slices + 1) * sizeof(*ctx->slice_offsets));

libavcodec/nvdec_hevc.c

@@ -274,11 +274,11 @@ static int nvdec_hevc_decode_slice(AVCodecContext *avctx, const uint8_t *buffer,
     NVDECContext *ctx = avctx->internal->hwaccel_priv_data;
     void *tmp;
 
-    tmp = av_fast_realloc(ctx->bitstream, &ctx->bitstream_allocated,
+    tmp = av_fast_realloc(ctx->bitstream_internal, &ctx->bitstream_allocated,
                           ctx->bitstream_len + size + 3);
     if (!tmp)
         return AVERROR(ENOMEM);
-    ctx->bitstream = tmp;
+    ctx->bitstream = ctx->bitstream_internal = tmp;
 
     tmp = av_fast_realloc(ctx->slice_offsets, &ctx->slice_offsets_allocated,
                           (ctx->nb_slices + 1) * sizeof(*ctx->slice_offsets));