avcodec/frame_thread_encoder: Free AVCodecContext structure on error during init

Fixes: MemLeak
Fixes: 8281
Fixes: PoC_option158.jpg
Fixes: CVE-2020-22037

Reviewed-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/frame_thread_encoder.c

@@ -126,7 +126,7 @@ int ff_frame_thread_encoder_init(AVCodecContext *avctx)
 {
     int i=0;
     ThreadContext *c;
-
+    AVCodecContext *thread_avctx = NULL;
 
     if(   !(avctx->thread_type & FF_THREAD_FRAME)
        || !(avctx->codec->capabilities & AV_CODEC_CAP_FRAME_THREADS))
@@ -202,16 +202,17 @@ int ff_frame_thread_encoder_init(AVCodecContext *avctx)
     for(i=0; i<avctx->thread_count ; i++){
         int ret;
         void *tmpv;
-        AVCodecContext *thread_avctx = avcodec_alloc_context3(avctx->codec);
+        thread_avctx = avcodec_alloc_context3(avctx->codec);
         if(!thread_avctx)
             goto fail;
         tmpv = thread_avctx->priv_data;
         *thread_avctx = *avctx;
+        thread_avctx->priv_data = tmpv;
+        thread_avctx->internal = NULL;
+        thread_avctx->hw_frames_ctx = NULL;
         ret = av_opt_copy(thread_avctx, avctx);
         if (ret < 0)
             goto fail;
-        thread_avctx->priv_data = tmpv;
-        thread_avctx->internal = NULL;
         if (avctx->codec->priv_class) {
             int ret = av_opt_copy(thread_avctx->priv_data, avctx->priv_data);
             if (ret < 0)
@@ -233,6 +234,8 @@ int ff_frame_thread_encoder_init(AVCodecContext *avctx)
 
     return 0;
 fail:
+    avcodec_close(thread_avctx);
+    av_freep(&thread_avctx);
     avctx->thread_count = i;
     av_log(avctx, AV_LOG_ERROR, "ff_frame_thread_encoder_init failed\n");
     ff_frame_thread_encoder_free(avctx);

libavcodec/frame_thread_encoder.h

@@ -23,6 +23,10 @@
 
 #include "avcodec.h"
 
+/**
+ * Initialize frame thread encoder.
+ * @note hardware encoders are not supported
+ */
 int ff_frame_thread_encoder_init(AVCodecContext *avctx);
 void ff_frame_thread_encoder_free(AVCodecContext *avctx);
 int ff_thread_video_encode_frame(AVCodecContext *avctx, AVPacket *pkt,