avformat/wtvdec: Check dir_length

Fixes: Infinite loop
Fixes: 26445/clusterfuzz-testcase-minimized-ffmpeg_dem_WTV_fuzzer-5125558331244544
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavformat/wtvdec.c b/libavformat/wtvdec.c
index 83f510b92f11e940409a3e15d568fa55dea809e6..77908e63921e88a48ac9743f0d67590f04fab237 100644 (file)
--- a/libavformat/wtvdec.c
+++ b/libavformat/wtvdec.c
@@ -273,6 +273,11 @@ static AVIOContext * wtvfile_open2(AVFormatContext *s, const uint8_t *buf, int b
                    "bad filename length, remaining directory entries ignored\n");
             break;
         }
+        if (dir_length == 0) {
+            av_log(s, AV_LOG_ERROR,
+                   "bad dir length, remaining directory entries ignored\n");
+            break;
+        }
         if (48 + (int64_t)name_size > buf_end - buf) {
             av_log(s, AV_LOG_ERROR, "filename exceeds buffer size; remaining directory entries ignored\n");
             break;