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security: fix integer overflow in loopback delay buffer allocation

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Memory Safety: Medium

In recalculate_buffer(), the buffer size computation
(delay + (1u<<15)) * 4 can overflow uint32_t when delay is large.
Additionally, the subsequent multiplication buffer_size * channels
for the realloc size can also overflow uint32_t, wrapping to a
small value and causing an undersized allocation. Later writes to
the buffer using the logical buffer_size would then overflow the
heap.

The delay value derives from rate * target_delay where both values
come from stream negotiation properties.

Fix by adding an overflow check on the delay computation and
widening the allocation size to size_t to prevent the second
overflow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Wim Taymans 2026-04-23 18:00:33 +02:00
parent 4305d7e82d
commit 1d68d7f2e9
1 changed files with 11 additions and 1 deletions
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12
src/modules/module-loopback.c
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@ -576,9 +576,18 @@ static void recalculate_buffer(struct impl *impl)
if (impl->target_delay > 0.0f && impl->channels > 0 && impl->rate > 0) { if (impl->target_delay > 0.0f && impl->channels > 0 && impl->rate > 0) {
uint32_t delay = (uint32_t)(impl->rate * impl->target_delay); uint32_t delay = (uint32_t)(impl->rate * impl->target_delay);
void *data; void *data;
size_t alloc_size;
if (delay > (UINT32_MAX / 4) - (1u<<15)) {
pw_log_warn("delay too large, delay disabled");
impl->buffer_size = 0;
free(impl->buffer_data);
impl->buffer_data = NULL;
goto done;
}
impl->buffer_size = (delay + (1u<<15)) * 4; impl->buffer_size = (delay + (1u<<15)) * 4;
data = realloc(impl->buffer_data, impl->buffer_size * impl->channels); alloc_size = (size_t)impl->buffer_size * impl->channels;
data = realloc(impl->buffer_data, alloc_size);
if (data == NULL) { if (data == NULL) {
pw_log_warn("can't allocate delay buffer, delay disabled: %m"); pw_log_warn("can't allocate delay buffer, delay disabled: %m");
impl->buffer_size = 0; impl->buffer_size = 0;
@ -591,6 +600,7 @@ static void recalculate_buffer(struct impl *impl)
free(impl->buffer_data); free(impl->buffer_data);
impl->buffer_data = NULL; impl->buffer_data = NULL;
} }
done:
pw_log_info("configured delay:%f buffer:%d", impl->target_delay, impl->buffer_size); pw_log_info("configured delay:%f buffer:%d", impl->target_delay, impl->buffer_size);
impl->recalc_delay = true; impl->recalc_delay = true;
} }