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avcodec/ffwavesynth: Simplify lcg_seek(), avoid negative case 

Fixes: negation of -9223372036854775808 cannot be represented in type 'int64_t' (aka 'long'); cast to an unsigned type to negate this value to itself
Fixes: 15289/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFWAVESYNTH_fuzzer-5709034499342336

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 2019-06-21 22:41:25 +02:00
parent cf2bd3ce79
commit 8c02209935
1 changed files with 3 additions and 9 deletions
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12
libavcodec/ffwavesynth.c
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@ -113,18 +113,12 @@ static uint32_t lcg_next(uint32_t *s)
return *s;
}
static void lcg_seek(uint32_t *s, int64_t dt)
static void lcg_seek(uint32_t *s, uint32_t dt)
{
uint32_t a, c, t = *s;
if (dt >= 0) {
a = LCG_A;
c = LCG_C;
} else { /* coefficients for a step backward */
a = LCG_AI;
c = (uint32_t)(-LCG_AI * LCG_C);
dt = -dt;
}
a = LCG_A;
c = LCG_C;
while (dt) {
if (dt & 1)
t = a * t + c;