[FFmpeg-cvslog] avcodec/pngdec: dont skip/read chunk twice

[Michael Niedermayer]

ffmpeg | branch: release/5.0 | Michael Niedermayer <michael at niedermayer.cc> | Wed Jan 11 23:56:05 2023 +0100| [904836c89fbb176f019816ccb32a3517acf6e8f6] | committer: Michael Niedermayer

avcodec/pngdec: dont skip/read chunk twice

Fixes: out of array access
Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PNG_fuzzer-6668158952144896.fuzz

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit df1a38d5200e14a29903f1027b4548d595c7ff8a)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=904836c89fbb176f019816ccb32a3517acf6e8f6
---

 libavcodec/pngdec.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 0bd2dbfca2..111afd9a4a 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -1229,6 +1229,7 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s,
                 }
                 av_log(avctx, AV_LOG_ERROR, ", skipping\n");
                 bytestream2_skip(&s->gb, length + 8); /* tag */
+                continue;
             }
         }
         tag = bytestream2_get_le32(&s->gb);