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libFLAC/bitreader.c: Fix shift invoking undefined behaviour

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Credit: Oss-Fuzz
Issue: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=19036
Testcase: fuzzer_decoder-5679084202098688
This commit is contained in:
Erik de Castro Lopo 2019-11-21 18:53:10 +11:00
parent f706f28322
commit d518e13a1f
1 changed files with 3 additions and 2 deletions
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5
src/libFLAC/bitreader.c
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@ -415,8 +415,9 @@ FLAC__bool FLAC__bitreader_read_raw_uint32(FLAC__BitReader *br, FLAC__uint32 *va
br->consumed_words++;
br->consumed_bits = 0;
if(bits) { /* if there are still bits left to read, there have to be less than 32 so they will all be in the next word */
*val = bits >= 32 ? 0 : *val << bits ;
*val |= (FLAC__uint32)(br->buffer[br->consumed_words] >> (FLAC__BITS_PER_WORD-bits));
uint32_t shift = FLAC__BITS_PER_WORD - bits;
*val = bits < 32 ? *val << bits : 0;
*val |= shift < FLAC__BITS_PER_WORD ? (FLAC__uint32)(br->buffer[br->consumed_words] >> shift) : 0;
br->consumed_bits = bits;
}
return true;