[FFmpeg-devel] [PATCH] avcodec/av1dec: Always set ret before goto end

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Before 0f8763fbea4e8816cd54c2a481d4c048fec58394, av1_frame_ref()
and update_reference_list() could fail and therefore needed to
be checked, which incidentally set ret. This is no longer happening,
leading to a potential use of an uninitialized value which is
also the subject of Coverity ticket #1596605.

Fix this by always setting ret before goto end; do not return
some random ancient value.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/av1dec.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
index 79a30a114d..c3f255a29a 100644
--- a/libavcodec/av1dec.c
+++ b/libavcodec/av1dec.c
@@ -1335,6 +1335,12 @@ static int av1_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
                     ret = set_output_frame(avctx, frame);
                     if (ret < 0)
                         av_log(avctx, AV_LOG_ERROR, "Set output frame error.\n");
+                } else {
+                    // CBS checks for us that the frame to be shown actually existed
+                    // in the bitstream; if it doesn't it could be e.g. due to
+                    // skip_frame setting. Return EAGAIN to indicate that we are
+                    // currently unable to produce output.
+                    ret = AVERROR(EAGAIN);
                 }
 
                 s->raw_frame_header = NULL;
@@ -1439,13 +1445,15 @@ static int av1_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
 
             update_reference_list(avctx);
 
-            if (s->raw_frame_header->show_frame && s->cur_frame.f) {
+            // cur_frame.f needn't exist due to skip_frame.
+            if (show_frame && s->cur_frame.f) {
                 ret = set_output_frame(avctx, frame);
                 if (ret < 0) {
                     av_log(avctx, AV_LOG_ERROR, "Set output frame error\n");
                     goto end;
                 }
-            }
+            } else
+                ret = AVERROR(EAGAIN);
             raw_tile_group = NULL;
             s->raw_frame_header = NULL;
             if (show_frame) {
-- 
2.40.1

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