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avcodec/mobiclip: Avoid signed integer overflows in idct()

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Fixes: signed integer overflow: 536870912 + 1610612736 cannot be represented in type 'int'
Fixes: 26288/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MOBICLIP_fuzzer-6194364759670784

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2020-10-16 17:55:26 +02:00
parent 6910e0f4e5
commit a4895b75a3
1 changed files with 10 additions and 9 deletions
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19
libavcodec/mobiclip.c
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@ -422,7 +422,8 @@ static void inverse4(unsigned *rs)
static void idct(int *arr, int size)
{
int e, f, g, h, x3, x2, x1, x0;
int e, f, g, h;
unsigned x3, x2, x1, x0;
int tmp[4];
if (size == 4) {
@ -437,14 +438,14 @@ static void idct(int *arr, int size)
inverse4(tmp);
e = arr[7] + arr[1] - arr[3] - (arr[3] >> 1);
f = arr[7] - arr[1] + arr[5] + (arr[5] >> 1);
g = arr[5] - arr[3] - arr[7] - (arr[7] >> 1);
h = arr[5] + arr[3] + arr[1] + (arr[1] >> 1);
x3 = g + (h >> 2);
x2 = e + (f >> 2);
x1 = (e >> 2) - f;
x0 = h - (g >> 2);
e = (unsigned)arr[7] + arr[1] - arr[3] - (arr[3] >> 1);
f = (unsigned)arr[7] - arr[1] + arr[5] + (arr[5] >> 1);
g = (unsigned)arr[5] - arr[3] - arr[7] - (arr[7] >> 1);
h = (unsigned)arr[5] + arr[3] + arr[1] + (arr[1] >> 1);
x3 = (unsigned)g + (h >> 2);
x2 = (unsigned)e + (f >> 2);
x1 = (e >> 2) - (unsigned)f;
x0 = (unsigned)h - (g >> 2);
arr[0] = tmp[0] + x0;
arr[1] = tmp[1] + x1;