From 7666d588ba1af26ce479e7fb92f7dc5b3a2ca48e Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Tue, 20 Apr 2021 17:40:56 +0200 Subject: [PATCH] avformat/mov: Avoid undefined overflow in time_offset calculation Fixes: signed integer overflow: 8511838621821575200 - -3954125146725285889 cannot be represented in type 'long' Fixes: 33414/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-6610119325515776 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Michael Niedermayer --- libavformat/mov.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/libavformat/mov.c b/libavformat/mov.c index 040babed95..3fc5a1e8ab 100644 --- a/libavformat/mov.c +++ b/libavformat/mov.c @@ -3817,7 +3817,11 @@ static void mov_build_index(MOVContext *mov, AVStream *st) if ((empty_duration || start_time) && mov->time_scale > 0) { if (empty_duration) empty_duration = av_rescale(empty_duration, sc->time_scale, mov->time_scale); - sc->time_offset = start_time - empty_duration; + + if (av_sat_sub64(start_time, empty_duration) != start_time - (uint64_t)empty_duration) + av_log(mov->fc, AV_LOG_WARNING, "start_time - empty_duration is not representable\n"); + + sc->time_offset = start_time - (uint64_t)empty_duration; sc->min_corrected_pts = start_time; if (!mov->advanced_editlist) current_dts = -sc->time_offset;