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multiply_frac wrong overflow #55

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multiply_frac wrong overflow #55

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37fa138
libspeexdsp: check for overflow in multiply_frac is too aggressive
Dec 23, 2025
7c12e2b
libspeexdsp: try to preserve valid internal state also if something f…
Dec 23, 2025
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48 changes: 43 additions & 5 deletions libspeexdsp/resample.c
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Original file line number Diff line number Diff line change
Expand Up @@ -594,11 +594,17 @@ static int multiply_frac(spx_uint32_t *result, spx_uint32_t value, spx_uint32_t
{
spx_uint32_t major = value / den;
spx_uint32_t remain = value % den;
/* TODO: Could use 64 bits operation to check for overflow. But only guaranteed in C99+ */
#if __STDC_VERSION__ >= 199901L
uint64_t r = (uint64_t)remain * (uint64_t)num / (uint64_t)den + (uint64_t)major * (uint64_t)num;
if (r > UINT32_MAX)
return RESAMPLER_ERR_OVERFLOW;
*result = (spx_uint32_t)r;
#else
if (remain > UINT32_MAX / num || major > UINT32_MAX / num
|| major * num > UINT32_MAX - remain * num / den)
return RESAMPLER_ERR_OVERFLOW;
*result = remain * num / den + major * num;
#endif
return RESAMPLER_ERR_SUCCESS;
}

Expand Down Expand Up @@ -1110,7 +1116,10 @@ static inline spx_uint32_t compute_gcd(spx_uint32_t a, spx_uint32_t b)
EXPORT int speex_resampler_set_rate_frac(SpeexResamplerState *st, spx_uint32_t ratio_num, spx_uint32_t ratio_den, spx_uint32_t in_rate, spx_uint32_t out_rate)
{
spx_uint32_t fact;
spx_uint32_t old_den;
spx_uint32_t old_in_rate = st->in_rate;
spx_uint32_t old_out_rate = st->out_rate;
spx_uint32_t old_num_rate = st->num_rate;
spx_uint32_t old_den = st->den_rate;
spx_uint32_t i;

if (ratio_num == 0 || ratio_den == 0)
Expand All @@ -1119,7 +1128,6 @@ EXPORT int speex_resampler_set_rate_frac(SpeexResamplerState *st, spx_uint32_t r
if (st->in_rate == in_rate && st->out_rate == out_rate && st->num_rate == ratio_num && st->den_rate == ratio_den)
return RESAMPLER_ERR_SUCCESS;

old_den = st->den_rate;
st->in_rate = in_rate;
st->out_rate = out_rate;
st->num_rate = ratio_num;
Expand All @@ -1130,20 +1138,50 @@ EXPORT int speex_resampler_set_rate_frac(SpeexResamplerState *st, spx_uint32_t r
st->num_rate /= fact;
st->den_rate /= fact;

if (old_den > 0)
spx_uint32_t samp_frac_num[st->nb_channels];
for (i=0;i<st->nb_channels;i++)
{
samp_frac_num[i] = st->samp_frac_num[i];
}
if ((old_den > 0) && (old_den != st->den_rate))
{
for (i=0;i<st->nb_channels;i++)
{
samp_frac_num[i] = st->samp_frac_num[i];
if (multiply_frac(&st->samp_frac_num[i],st->samp_frac_num[i],st->den_rate,old_den) != RESAMPLER_ERR_SUCCESS)
{
for (spx_uint32_t j=0;j<=i;j++)
{
st->samp_frac_num[j] = samp_frac_num[j];
}
st->in_rate = old_in_rate;
st->out_rate = old_out_rate;
st->num_rate = old_num_rate;
st->den_rate = old_den;
return RESAMPLER_ERR_OVERFLOW;
}
/* Safety net */
if (st->samp_frac_num[i] >= st->den_rate)
st->samp_frac_num[i] = st->den_rate-1;
}
}

if (st->initialised)
return update_filter(st);
{
int r = update_filter(st);
if (r != RESAMPLER_ERR_SUCCESS)
{
for (i=0;i<st->nb_channels;i++)
{
st->samp_frac_num[i] = samp_frac_num[i];
}
st->in_rate = old_in_rate;
st->out_rate = old_out_rate;
st->num_rate = old_num_rate;
st->den_rate = old_den;
return r;
}
}
return RESAMPLER_ERR_SUCCESS;
}

Expand Down