ffmpeg: fix for CVE-2022-48434

libavcodec/pthread_frame.c in FFmpeg before 5.1.2, as used in VLC and
other products, leaves stale hwaccel state in worker threads, which
allows attackers to trigger a use-after-free and execute arbitrary
code in some circumstances (e.g., hardware re-initialization upon a
mid-video SPS change when Direct3D11 is used).

(From OE-Core rev: 392f984ffd95bcd3ce4c364b40425e7808ca7719)

Signed-off-by: Narpat Mali <narpat.mali@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

2 files changed, 132 insertions, 1 deletions

diff --git a/meta/recipes-multimedia/ffmpeg/ffmpeg/CVE-2022-48434.patch b/meta/recipes-multimedia/ffmpeg/ffmpeg/CVE-2022-48434.patch
new file mode 100644
index 0000000000..3cd374dc39
--- /dev/null
+++ b/meta/recipes-multimedia/ffmpeg/ffmpeg/CVE-2022-48434.patch
@@ -0,0 +1,130 @@
+From e40c964a0678908e2c756741343ed50d6a99ee12 Mon Sep 17 00:00:00 2001
+From: Anton Khirnov <anton@khirnov.net>
+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 <narpat.mali@windriver.com>
+---
+ 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
+
diff --git a/meta/recipes-multimedia/ffmpeg/ffmpeg_5.0.1.bb b/meta/recipes-multimedia/ffmpeg/ffmpeg_5.0.1.bb
index 4bcbda9976..6ece34fcfd 100644
--- a/meta/recipes-multimedia/ffmpeg/ffmpeg_5.0.1.bb
+++ b/meta/recipes-multimedia/ffmpeg/ffmpeg_5.0.1.bb
@@ -28,7 +28,8 @@ SRC_URI = "https://www.ffmpeg.org/releases/${BP}.tar.xz \
            file://0001-avcodec-smcenc-stop-accessing-out-of-bounds-frame.patch \
            file://0001-avcodec-vp3-Add-missing-check-for-av_malloc.patch \
            file://0001-avformat-nutdec-Add-check-for-avformat_new_stream.patch \
-           "
+           file://CVE-2022-48434.patch \
+          "
 
 SRC_URI[sha256sum] = "ef2efae259ce80a240de48ec85ecb062cecca26e4352ffb3fda562c21a93007b"