[FFmpeg-devel] [PATCH] vp9: fix a race in exporting encoding parameters

[Anton Khirnov]

Modifying shared state after ff_thread_finish_setup() is not allowed, so
set the encoding parameters directly on the output frame.

Found-by: James Almer <jamrial at gmail.com>
---
 libavcodec/vp9.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/libavcodec/vp9.c b/libavcodec/vp9.c
index 4659f94ee8..46062f8a8f 100644
--- a/libavcodec/vp9.c
+++ b/libavcodec/vp9.c
@@ -1499,7 +1499,8 @@ int loopfilter_proc(AVCodecContext *avctx)
 }
 #endif
 
-static int vp9_export_enc_params(VP9Context *s, VP9Frame *frame)
+static int vp9_export_enc_params(VP9Context *s, AVFrame *frame_dst,
+                                 const VP9Frame *frame)
 {
     AVVideoEncParams *par;
     unsigned int tile, nb_blocks = 0;
@@ -1509,7 +1510,7 @@ static int vp9_export_enc_params(VP9Context *s, VP9Frame *frame)
             nb_blocks += s->td[tile].nb_block_structure;
     }
 
-    par = av_video_enc_params_create_side_data(frame->tf.f,
+    par = av_video_enc_params_create_side_data(frame_dst,
         AV_VIDEO_ENC_PARAMS_VP9, nb_blocks);
     if (!par)
         return AVERROR(ENOMEM);
@@ -1759,12 +1760,6 @@ FF_ENABLE_DEPRECATION_WARNINGS
         s->td->error_info = 0;
         return AVERROR_INVALIDDATA;
     }
-    if (avctx->export_side_data & AV_CODEC_EXPORT_DATA_VIDEO_ENC_PARAMS) {
-        ret = vp9_export_enc_params(s, &s->s.frames[CUR_FRAME]);
-        if (ret < 0)
-            return ret;
-    }
-
 finish:
     // ref frame setup
     for (i = 0; i < 8; i++) {
@@ -1778,6 +1773,13 @@ finish:
     if (!s->s.h.invisible) {
         if ((ret = av_frame_ref(frame, s->s.frames[CUR_FRAME].tf.f)) < 0)
             return ret;
+
+        if (avctx->export_side_data & AV_CODEC_EXPORT_DATA_VIDEO_ENC_PARAMS) {
+            ret = vp9_export_enc_params(s, frame, &s->s.frames[CUR_FRAME]);
+            if (ret < 0)
+                return ret;
+        }
+
         *got_frame = 1;
     }
 
-- 
2.28.0