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apv_decode: Discard invalid run codes earlier

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Caught by ubsan - would cause an invalid shift in constructing the
run value.
This commit is contained in:
Mark Thompson
2025-05-13 20:50:38 +01:00
parent 1753d41d4e
commit 527d5eaec7
1 changed files with 14 additions and 0 deletions
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14
libavcodec/apv_entropy.c
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@@ -278,6 +278,13 @@ int ff_apv_entropy_decode_block(int16_t *restrict coeff,
bits = next_bits & 0xffff; bits = next_bits & 0xffff;
// Determine code length. // Determine code length.
leading_zeroes = 15 - av_log2(bits); leading_zeroes = 15 - av_log2(bits);
if (leading_zeroes >= 6) {
// 6 zeroes implies run > 64, which is always invalid.
av_log(state->log_ctx, AV_LOG_ERROR,
"Out-of-range run value: %d leading zeroes.\n",
leading_zeroes);
return AVERROR_INVALIDDATA;
}
// Extract the low bits. // Extract the low bits.
low_bit_count = leading_zeroes; low_bit_count = leading_zeroes;
low_bit_shift = 16 - (1 + 2 * leading_zeroes); low_bit_shift = 16 - (1 + 2 * leading_zeroes);
@@ -443,6 +450,13 @@ int ff_apv_entropy_decode_block(int16_t *restrict coeff,
bits = next_bits & 0xffff; bits = next_bits & 0xffff;
// Determine code length. // Determine code length.
leading_zeroes = 15 - av_log2(bits); leading_zeroes = 15 - av_log2(bits);
if (leading_zeroes >= 6) {
// 6 zeroes implies run > 64, which is always invalid.
av_log(state->log_ctx, AV_LOG_ERROR,
"Out-of-range run value: %d leading zeroes.\n",
leading_zeroes);
return AVERROR_INVALIDDATA;
}
// Extract the low bits. // Extract the low bits.
low_bit_count = leading_zeroes + k_run; low_bit_count = leading_zeroes + k_run;
low_bit_shift = 16 - (1 + 2 * leading_zeroes + k_run); low_bit_shift = 16 - (1 + 2 * leading_zeroes + k_run);