From: "Ronald S. Bultje" <[email protected]> On 2012-03-26 14:54:56 -0700, Ronald S. Bultje wrote: > From: "Ronald S. Bultje" <[email protected]> > > This will (in ER) write to the pic->mb_type[] array of the previous > image, which may in a subsequent thread already have been re-used for a > new image, thus causing two threads to write to the same pic->mb_type[] > array, causing a race condition which can crash in rv34_decode_cbp(), > called by rv34_decode_inter_mb_header() (which accesses mb_type[] twice, > assuming values are maintained, which the race condition breaks).
Analysis is correct, I think setting s->mb_num_left to 0 after running ER is cleaner since it also prevents running ER twice on the same frame when single threaded. Janne ---8<--- Prevents running error resilience on a previous frame which will write to the pic->mb_type[] array of the previous image. The array might already be re-used for a new image in a subsequent thread, thus cause two threads to write to the same pic->mb_type[] array, causing a race condition which can crash in rv34_decode_cbp(), called by rv34_decode_inter_mb_header() (which accesses mb_type[] twice, assuming values are maintained, which the race condition breaks). Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind CC: [email protected] --- libavcodec/rv34.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/libavcodec/rv34.c b/libavcodec/rv34.c index da5d437..b366ead 100644 --- a/libavcodec/rv34.c +++ b/libavcodec/rv34.c @@ -1576,6 +1576,7 @@ static int finish_frame(AVCodecContext *avctx, AVFrame *pict) ff_er_frame_end(s); ff_MPV_frame_end(s); + s->mb_num_left = 0; if (HAVE_THREADS && (s->avctx->active_thread_type & FF_THREAD_FRAME)) ff_thread_report_progress(&s->current_picture_ptr->f, INT_MAX, 0); @@ -1774,6 +1775,7 @@ int ff_rv34_decode_frame(AVCodecContext *avctx, * only complete frames */ ff_er_frame_end(s); ff_MPV_frame_end(s); + s->mb_num_left = 0; ff_thread_report_progress(&s->current_picture_ptr->f, INT_MAX, 0); return AVERROR_INVALIDDATA; } -- 1.7.8.5 _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
