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avutil/lfg: Correct index increment type to avoid undefined behavior 

Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
Fixes: 18333/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_COMFORTNOISE_fuzzer-5668481831272448

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 6014bcf1b7)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2019-10-19 21:27:41 +02:00
parent 3a6ef19263
commit f0bd54aaa7
1 changed files with 6 additions and 3 deletions
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9
libavutil/lfg.h
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@ -51,8 +51,9 @@ int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length);
* it may be good enough and faster for your specific use case. * it may be good enough and faster for your specific use case.
*/ */
static inline unsigned int av_lfg_get(AVLFG *c){ static inline unsigned int av_lfg_get(AVLFG *c){
c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; unsigned a = c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
return c->state[c->index++ & 63]; c->index += 1U;
return a;
} }
/** /**
@ -63,7 +64,9 @@ static inline unsigned int av_lfg_get(AVLFG *c){
static inline unsigned int av_mlfg_get(AVLFG *c){ static inline unsigned int av_mlfg_get(AVLFG *c){
unsigned int a= c->state[(c->index-55) & 63]; unsigned int a= c->state[(c->index-55) & 63];
unsigned int b= c->state[(c->index-24) & 63]; unsigned int b= c->state[(c->index-24) & 63];
return c->state[c->index++ & 63] = 2*a*b+a+b; a = c->state[c->index & 63] = 2*a*b+a+b;
c->index += 1U;
return a;
} }
/** /**