[FFmpeg-devel] [PATCH 1/2] avformat/mov: Avoid overflow in dts

[FFmpeg-devel] [PATCH 1/2] avformat/mov: Avoid overflow in dts

[Michael Niedermayer]

This basically ignores the overflow without undefined behavior, alternatively we could detect and error out

Fixes: signed integer overflow: 6310596683470275584 + 7660622966157213696 cannot be represented in type 'long'
Fixes: 70433/clusterfuzz-testcase-minimized-ffmpeg_IO_DEMUXER_fuzzer-5483347233538048

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/mov.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index b74e43e2140..403af1bba17 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -3472,10 +3472,10 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
             sc->stts_data[i].duration = 1;
             corrected_dts += (delta_magnitude < 0 ? (int64_t)delta_magnitude : 1) * sample_count;
         } else {
-            corrected_dts += sample_duration * (int64_t)sample_count;
+            corrected_dts += sample_duration * (uint64_t)sample_count;
         }
 
-        current_dts += sc->stts_data[i].duration * (int64_t)sample_count;
+        current_dts += sc->stts_data[i].duration * (uint64_t)sample_count;
 
         if (current_dts > corrected_dts) {
             int64_t drift = (current_dts - corrected_dts)/FFMAX(sample_count, 1);
-- 
2.45.2

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[FFmpeg-devel] [PATCH 2/2] avformat/matroskadec: Check desc_bytes so bits fit in 64bit

[Michael Niedermayer]

Likely a tighter check can be done

Fixes: signed integer overflow: 3305606804154370442 * 8 cannot be represented in type 'long'
Fixes: 70449/clusterfuzz-testcase-minimized-ffmpeg_dem_WEBM_DASH_MANIFEST_fuzzer-4771166007918592

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/matroskadec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index aa28a37da4c..175d6a3ef61 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -4633,7 +4633,7 @@ static int64_t webm_dash_manifest_compute_bandwidth(AVFormatContext *s, int64_t
                 int64_t desc_bytes = desc_end.end_offset - desc_beg.start_offset;
                 int64_t desc_ns = desc_end.end_time_ns - desc_beg.start_time_ns;
                 double desc_sec, calc_bits_per_second, percent, mod_bits_per_second;
-                if (desc_bytes <= 0)
+                if (desc_bytes <= 0 || desc_bytes > INT64_MAX/8)
                     return -1;
 
                 desc_sec = desc_ns / nano_seconds_per_second;
-- 
2.45.2

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