[FFmpeg-devel] [PATCH 1/2] avformat/vividas: Check packet size

[Michael Niedermayer]

Fixes: signed integer overflow: 119760682 - -2084600173 cannot be represented in type 'int'
Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_VIVIDAS_fuzzer-6745781167587328

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavformat/vividas.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/libavformat/vividas.c b/libavformat/vividas.c
index e9954f73ed0..e8efe49a5c0 100644
--- a/libavformat/vividas.c
+++ b/libavformat/vividas.c
@@ -683,6 +683,7 @@ static int viv_read_packet(AVFormatContext *s,
 
     if (viv->sb_entries[viv->current_sb_entry].flag == 0) {
         uint64_t v_size = ffio_read_varlen(pb);
+        int last, last_start;
 
         if (!viv->num_audio)
             return AVERROR_INVALIDDATA;
@@ -704,14 +705,22 @@ static int viv_read_packet(AVFormatContext *s,
             start = ffio_read_varlen(pb);
             pcm_bytes = ffio_read_varlen(pb);
 
-            if (i > 0 && start == 0)
-                break;
+            if (i > 0) {
+                if (start == 0)
+                    break;
+                if (start < last || start - (unsigned)last > INT_MAX)
+                    return AVERROR_INVALIDDATA;
+            }
 
             viv->n_audio_subpackets = i + 1;
+            last =
             viv->audio_subpackets[i].start = start;
             viv->audio_subpackets[i].pcm_bytes = pcm_bytes;
         }
+        last_start =
         viv->audio_subpackets[viv->n_audio_subpackets].start = (int)(off - avio_tell(pb));
+        if (last_start < last || last_start - (unsigned)last > INT_MAX)
+            return AVERROR_INVALIDDATA;
         viv->current_audio_subpacket = 0;
 
     } else {
-- 
2.17.1