Re: [FFmpeg-devel] [PATCH 5/9] avformat/mov: Check extend and base offset - Rémi Denis-Courmont

From: "Rémi Denis-Courmont" <remi@remlab.net>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 5/9] avformat/mov: Check extend and base offset
Date: Tue, 18 Jun 2024 09:07:10 +0200
Message-ID: <148B64A1-B7B1-400D-B64B-C9FF8043CDEB@remlab.net> (raw)
In-Reply-To: <20240616230831.912377-5-michael@niedermayer.cc>

Le 17 juin 2024 01:08:27 GMT+02:00, Michael Niedermayer <michael@niedermayer.cc> a écrit :
>Fixes: signed integer overflow: 2314885530818453536 + 9151314442816847872 cannot be represented in type 'long'
>Fixes: 68359/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-6571950311800832
>
>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, 3 insertions(+), 1 deletion(-)
>
>diff --git a/libavformat/mov.c b/libavformat/mov.c
>index 9016cd5ad08..46cbce98040 100644
>--- a/libavformat/mov.c
>+++ b/libavformat/mov.c
>@@ -8131,7 +8131,9 @@ static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>         }
>         for (int j = 0; j < extent_count; j++) {
>             if (rb_size(pb, &extent_offset, offset_size) < 0 ||
>-                rb_size(pb, &extent_length, length_size) < 0)
>+                rb_size(pb, &extent_length, length_size) < 0 ||
>+                base_offset < 0 || extent_offset < 0 ||
>+                base_offset + (uint64_t)extent_offset > INT64_MAX)

Can we please stop with the bespoke arithmetic overflow checks and add dedicated helpers instead, similar to what GCC and C23 have?

>                 return AVERROR_INVALIDDATA;
>             if (offset_type == 1)
>                 c->heif_item[i].is_idat_relative = 1;
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