avcodec/pgssubdec: Check for duplicate display segments

In such a duplication the previous gets overwritten and leaks

Fixes: memleak
Fixes: 12510/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PGSSUB_fuzzer-5694439226343424
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/pgssubdec.c b/libavcodec/pgssubdec.c
index b897d72aab351c9002f3642f0e4927671493d984..8c10f6d5733138e8ed0b6557214ead79e1822ef5 100644 (file)
--- a/libavcodec/pgssubdec.c
+++ b/libavcodec/pgssubdec.c
@@ -676,6 +676,11 @@ static int decode(AVCodecContext *avctx, void *data, int *data_size,
              */
             break;
         case DISPLAY_SEGMENT:
+            if (*data_size) {
+                av_log(avctx, AV_LOG_ERROR, "Duplicate display segment\n");
+                ret = AVERROR_INVALIDDATA;
+                break;
+            }
             ret = display_end_segment(avctx, data, buf, segment_length);
             if (ret >= 0)
                 *data_size = ret;