From e40c964a0678908e2c756741343ed50d6a99ee12 Mon Sep 17 00:00:00 2001 From: Anton Khirnov Date: Fri, 28 Apr 2023 11:45:30 +0000 Subject: [PATCH] lavc/pthread_frame: avoid leaving stale hwaccel state in worker threads This state is not refcounted, so make sure it always has a well-defined owner. Remove the block added in 091341f, as this commit also solves that issue in a more general way. CVE:CVE-2022-48434 Upstream-Status: Backport [https://github.com/FFmpeg/FFmpeg/commit/cc867f2c09d2b69cee8a0eccd62aff002cbbfe11] Signed-off-by: Narpat Mali --- libavcodec/pthread_frame.c | 46 +++++++++++++++++++++++++++++--------- 1 file changed, 35 insertions(+), 11 deletions(-) diff --git a/libavcodec/pthread_frame.c b/libavcodec/pthread_frame.c index 85a6bc9..e40dced 100644 --- a/libavcodec/pthread_frame.c +++ b/libavcodec/pthread_frame.c @@ -145,6 +145,12 @@ typedef struct FrameThreadContext { * Set for the first N packets, where N is the number of threads. * While it is set, ff_thread_en/decode_frame won't return any results. */ + + /* hwaccel state is temporarily stored here in order to transfer its ownership + * to the next decoding thread without the need for extra synchronization */ + const AVHWAccel *stash_hwaccel; + void *stash_hwaccel_context; + void *stash_hwaccel_priv; } FrameThreadContext; #if FF_API_THREAD_SAFE_CALLBACKS @@ -229,9 +235,17 @@ FF_ENABLE_DEPRECATION_WARNINGS ff_thread_finish_setup(avctx); if (p->hwaccel_serializing) { + /* wipe hwaccel state to avoid stale pointers lying around; + * the state was transferred to FrameThreadContext in + * ff_thread_finish_setup(), so nothing is leaked */ + avctx->hwaccel = NULL; + avctx->hwaccel_context = NULL; + avctx->internal->hwaccel_priv_data = NULL; + p->hwaccel_serializing = 0; pthread_mutex_unlock(&p->parent->hwaccel_mutex); } + av_assert0(!avctx->hwaccel); if (p->async_serializing) { p->async_serializing = 0; @@ -294,14 +308,10 @@ static int update_context_from_thread(AVCodecContext *dst, AVCodecContext *src, dst->color_range = src->color_range; dst->chroma_sample_location = src->chroma_sample_location; - dst->hwaccel = src->hwaccel; - dst->hwaccel_context = src->hwaccel_context; - dst->channels = src->channels; dst->sample_rate = src->sample_rate; dst->sample_fmt = src->sample_fmt; dst->channel_layout = src->channel_layout; - dst->internal->hwaccel_priv_data = src->internal->hwaccel_priv_data; if (!!dst->hw_frames_ctx != !!src->hw_frames_ctx || (dst->hw_frames_ctx && dst->hw_frames_ctx->data != src->hw_frames_ctx->data)) { @@ -442,6 +452,12 @@ static int submit_packet(PerThreadContext *p, AVCodecContext *user_avctx, pthread_mutex_unlock(&p->mutex); return err; } + + /* transfer hwaccel state stashed from previous thread, if any */ + av_assert0(!p->avctx->hwaccel); + FFSWAP(const AVHWAccel*, p->avctx->hwaccel, fctx->stash_hwaccel); + FFSWAP(void*, p->avctx->hwaccel_context, fctx->stash_hwaccel_context); + FFSWAP(void*, p->avctx->internal->hwaccel_priv_data, fctx->stash_hwaccel_priv); } av_packet_unref(p->avpkt); @@ -647,6 +663,14 @@ void ff_thread_finish_setup(AVCodecContext *avctx) { async_lock(p->parent); } + /* save hwaccel state for passing to the next thread; + * this is done here so that this worker thread can wipe its own hwaccel + * state after decoding, without requiring synchronization */ + av_assert0(!p->parent->stash_hwaccel); + p->parent->stash_hwaccel = avctx->hwaccel; + p->parent->stash_hwaccel_context = avctx->hwaccel_context; + p->parent->stash_hwaccel_priv = avctx->internal->hwaccel_priv_data; + pthread_mutex_lock(&p->progress_mutex); if(atomic_load(&p->state) == STATE_SETUP_FINISHED){ av_log(avctx, AV_LOG_WARNING, "Multiple ff_thread_finish_setup() calls\n"); @@ -700,13 +724,6 @@ void ff_frame_thread_free(AVCodecContext *avctx, int thread_count) park_frame_worker_threads(fctx, thread_count); - if (fctx->prev_thread && avctx->internal->hwaccel_priv_data != - fctx->prev_thread->avctx->internal->hwaccel_priv_data) { - if (update_context_from_thread(avctx, fctx->prev_thread->avctx, 1) < 0) { - av_log(avctx, AV_LOG_ERROR, "Failed to update user thread.\n"); - } - } - if (fctx->prev_thread && fctx->prev_thread != fctx->threads) if (update_context_from_thread(fctx->threads->avctx, fctx->prev_thread->avctx, 0) < 0) { av_log(avctx, AV_LOG_ERROR, "Final thread update failed\n"); @@ -760,6 +777,13 @@ void ff_frame_thread_free(AVCodecContext *avctx, int thread_count) av_freep(&fctx->threads); ff_pthread_free(fctx, thread_ctx_offsets); + /* if we have stashed hwaccel state, move it to the user-facing context, + * so it will be freed in avcodec_close() */ + av_assert0(!avctx->hwaccel); + FFSWAP(const AVHWAccel*, avctx->hwaccel, fctx->stash_hwaccel); + FFSWAP(void*, avctx->hwaccel_context, fctx->stash_hwaccel_context); + FFSWAP(void*, avctx->internal->hwaccel_priv_data, fctx->stash_hwaccel_priv); + av_freep(&avctx->internal->thread_ctx); } -- 2.40.0