[FFmpeg-devel] [PATCH] avcodec/nvdec: don't attempt to free NVDECContext->bitstream on simple decode_slice hwaccels
James Almer
jamrial at gmail.com
Wed Feb 7 00:58:49 EET 2024
On 2/6/2024 7:14 PM, Andreas Rheinhardt wrote:
> James Almer:
>> If FFHWAccel->end_frame() isn't called before FFHWAccel->uninit(), an attempt
>> to free a stale pointer could take place.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>> libavcodec/nvdec.c | 9 +++++++++
>> libavcodec/nvdec.h | 1 +
>> libavcodec/nvdec_mjpeg.c | 2 +-
>> libavcodec/nvdec_mpeg12.c | 4 ++--
>> libavcodec/nvdec_mpeg4.c | 2 +-
>> libavcodec/nvdec_vc1.c | 4 ++--
>> libavcodec/nvdec_vp8.c | 2 +-
>> libavcodec/nvdec_vp9.c | 2 +-
>> 8 files changed, 18 insertions(+), 8 deletions(-)
>>
>> diff --git a/libavcodec/nvdec.c b/libavcodec/nvdec.c
>> index 27be644356..8a7f5c0dac 100644
>> --- a/libavcodec/nvdec.c
>> +++ b/libavcodec/nvdec.c
>> @@ -274,6 +274,15 @@ int ff_nvdec_decode_uninit(AVCodecContext *avctx)
>> return 0;
>> }
>>
>> +int ff_nvdec_simple_decode_uninit(AVCodecContext *avctx)
>> +{
>> + NVDECContext *ctx = avctx->internal->hwaccel_priv_data;
>> +
>> + ctx->bitstream = NULL;
>> +
>> + return ff_nvdec_decode_uninit(avctx);
>> +}
>> +
>> static void nvdec_free_dummy(struct AVHWFramesContext *ctx)
>> {
>> av_buffer_pool_uninit(&ctx->pool);
>> diff --git a/libavcodec/nvdec.h b/libavcodec/nvdec.h
>> index 353e95bf42..83bc1de84c 100644
>> --- a/libavcodec/nvdec.h
>> +++ b/libavcodec/nvdec.h
>> @@ -73,6 +73,7 @@ int ff_nvdec_decode_uninit(AVCodecContext *avctx);
>> int ff_nvdec_start_frame(AVCodecContext *avctx, AVFrame *frame);
>> int ff_nvdec_start_frame_sep_ref(AVCodecContext *avctx, AVFrame *frame, int has_sep_ref);
>> int ff_nvdec_end_frame(AVCodecContext *avctx);
>> +int ff_nvdec_simple_decode_uninit(AVCodecContext *avctx);
>> int ff_nvdec_simple_end_frame(AVCodecContext *avctx);
>> int ff_nvdec_simple_decode_slice(AVCodecContext *avctx, const uint8_t *buffer,
>> uint32_t size);
>> diff --git a/libavcodec/nvdec_mjpeg.c b/libavcodec/nvdec_mjpeg.c
>> index 850634bf1a..adef21b0f7 100644
>> --- a/libavcodec/nvdec_mjpeg.c
>> +++ b/libavcodec/nvdec_mjpeg.c
>> @@ -80,6 +80,6 @@ const FFHWAccel ff_mjpeg_nvdec_hwaccel = {
>> .decode_slice = nvdec_mjpeg_decode_slice,
>> .frame_params = nvdec_mjpeg_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>> diff --git a/libavcodec/nvdec_mpeg12.c b/libavcodec/nvdec_mpeg12.c
>> index a4603c7ea7..5d100a46ba 100644
>> --- a/libavcodec/nvdec_mpeg12.c
>> +++ b/libavcodec/nvdec_mpeg12.c
>> @@ -110,7 +110,7 @@ const FFHWAccel ff_mpeg2_nvdec_hwaccel = {
>> .decode_slice = ff_nvdec_simple_decode_slice,
>> .frame_params = nvdec_mpeg12_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>> #endif
>> @@ -126,7 +126,7 @@ const FFHWAccel ff_mpeg1_nvdec_hwaccel = {
>> .decode_slice = ff_nvdec_simple_decode_slice,
>> .frame_params = nvdec_mpeg12_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>> #endif
>> diff --git a/libavcodec/nvdec_mpeg4.c b/libavcodec/nvdec_mpeg4.c
>> index 20a0499437..5a50f7d77f 100644
>> --- a/libavcodec/nvdec_mpeg4.c
>> +++ b/libavcodec/nvdec_mpeg4.c
>> @@ -120,6 +120,6 @@ const FFHWAccel ff_mpeg4_nvdec_hwaccel = {
>> .decode_slice = nvdec_mpeg4_decode_slice,
>> .frame_params = nvdec_mpeg4_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>> diff --git a/libavcodec/nvdec_vc1.c b/libavcodec/nvdec_vc1.c
>> index 5096d784df..e9ab16c63d 100644
>> --- a/libavcodec/nvdec_vc1.c
>> +++ b/libavcodec/nvdec_vc1.c
>> @@ -124,7 +124,7 @@ const FFHWAccel ff_vc1_nvdec_hwaccel = {
>> .decode_slice = ff_nvdec_simple_decode_slice,
>> .frame_params = nvdec_vc1_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>>
>> @@ -139,7 +139,7 @@ const FFHWAccel ff_wmv3_nvdec_hwaccel = {
>> .decode_slice = ff_nvdec_simple_decode_slice,
>> .frame_params = nvdec_vc1_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>> #endif
>> diff --git a/libavcodec/nvdec_vp8.c b/libavcodec/nvdec_vp8.c
>> index ff3b3f259c..bbea6f1577 100644
>> --- a/libavcodec/nvdec_vp8.c
>> +++ b/libavcodec/nvdec_vp8.c
>> @@ -101,6 +101,6 @@ const FFHWAccel ff_vp8_nvdec_hwaccel = {
>> .decode_slice = ff_nvdec_simple_decode_slice,
>> .frame_params = nvdec_vp8_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>> diff --git a/libavcodec/nvdec_vp9.c b/libavcodec/nvdec_vp9.c
>> index e196391c6d..69b12657b6 100644
>> --- a/libavcodec/nvdec_vp9.c
>> +++ b/libavcodec/nvdec_vp9.c
>> @@ -180,6 +180,6 @@ const FFHWAccel ff_vp9_nvdec_hwaccel = {
>> .decode_slice = ff_nvdec_simple_decode_slice,
>> .frame_params = nvdec_vp9_frame_params,
>> .init = ff_nvdec_decode_init,
>> - .uninit = ff_nvdec_decode_uninit,
>> + .uninit = ff_nvdec_simple_decode_uninit,
>> .priv_data_size = sizeof(NVDECContext),
>> };
>
> Using a field for both an ownership pointer and as a pure data pointer
> is bad and confusing. IMO there should be different pointers for this;
> or rather: bitstream is always set and used as data pointer and the
> another pointer for ownership which may alias bitstream. In fact, it
> looks like this is exactly what bitstream_internal is, it is just not
> used by H.264 and HEVC in this manner (they use bitstream for allocated
> stuff).
Yeah, whereas AV1 is doing it right.
Sent a new version with this approach. Thanks for the review.
> With the approach outlined above, ff_nvdec_simple_end_frame() might
> become obsolete.
>
> - Andreas
>
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