[FFmpeg-devel] [PATCH 3/5] avformat/avidec: Use av_sat_sub64() in check_stream_max_drift()

[Michael Niedermayer]

Fixes: signed integer overflow: 8833900919969684211 - -9223372036854775808 cannot be represented in type 'long'
Fixes: 26726/clusterfuzz-testcase-minimized-ffmpeg_dem_AVI_fuzzer-5669377724383232
Fixes: 27587/clusterfuzz-testcase-minimized-ffmpeg_dem_AVI_fuzzer-6294562263531520

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/avidec.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libavformat/avidec.c b/libavformat/avidec.c
index 7e527e15ee..57dc54452b 100644
--- a/libavformat/avidec.c
+++ b/libavformat/avidec.c
@@ -1691,18 +1691,19 @@ static int check_stream_max_drift(AVFormatContext *s)
             AVIStream *ast = st->priv_data;
 
             if (idx[i] && min_dts != INT64_MAX / 2) {
-                int64_t dts;
+                int64_t dts, delta_dts;
                 dts = av_rescale_q(st->internal->index_entries[idx[i] - 1].timestamp /
                                    FFMAX(ast->sample_size, 1),
                                    st->time_base, AV_TIME_BASE_Q);
+                delta_dts = av_sat_sub64(dts, min_dts);
                 max_dts = FFMAX(max_dts, dts);
                 max_buffer = FFMAX(max_buffer,
-                                   av_rescale(dts - min_dts,
+                                   av_rescale(delta_dts,
                                               st->codecpar->bit_rate,
                                               AV_TIME_BASE));
             }
         }
-        if (max_dts - min_dts > 2 * AV_TIME_BASE ||
+        if (av_sat_sub64(max_dts, min_dts) > 2 * AV_TIME_BASE ||
             max_buffer > 1024 * 1024 * 8 * 8) {
             av_free(idx);
             return 1;
-- 
2.17.1