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hw/audio/hda-codec: fix multiplication overflow

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After a relatively short time, there is an multiplication overflow
when multiplying (now - buft_start) with hda_bytes_per_second().
While the uptime now - buft_start only overflows after 2**63 ns
= 292.27 years, this happens hda_bytes_per_second() times faster
with the multiplication. At 44100 samples/s * 2 channels
* 2 bytes/channel = 176400 bytes/s that is 14.52 hours. After the
multiplication overflow the affected audio stream stalls.

Replace the multiplication and following division with muldiv64()
to prevent a multiplication overflow.

Fixes: 280c1e1cdb ("audio/hda: create millisecond timers that handle IO")
Reported-by: M_O_Bz <m_o_bz@163.com>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-Id: <20231105172552.8405-1-vr_qemu@t-online.de>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Volker Rümelin 2023-11-05 18:25:51 +01:00 committed by Michael S. Tsirkin
parent c44f4263b2
commit 74e8593e7e
1 changed files with 21 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
hw/audio/hda-codec.c
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@ -22,6 +22,7 @@
#include "hw/qdev-properties.h"
#include "intel-hda.h"
#include "migration/vmstate.h"
#include "qemu/host-utils.h"
#include "qemu/module.h"
#include "intel-hda-defs.h"
#include "audio/audio.h"
@ -189,9 +190,9 @@ struct HDAAudioState {
bool use_timer;
};
static inline int64_t hda_bytes_per_second(HDAAudioStream *st)
static inline uint32_t hda_bytes_per_second(HDAAudioStream *st)
{
return 2LL * st->as.nchannels * st->as.freq;
return 2 * (uint32_t)st->as.nchannels * (uint32_t)st->as.freq;
}
static inline void hda_timer_sync_adjust(HDAAudioStream *st, int64_t target_pos)
@ -222,12 +223,18 @@ static void hda_audio_input_timer(void *opaque)
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
int64_t buft_start = st->buft_start;
int64_t uptime = now - st->buft_start;
int64_t wpos = st->wpos;
int64_t rpos = st->rpos;
int64_t wanted_rpos;
int64_t wanted_rpos = hda_bytes_per_second(st) * (now - buft_start)
/ NANOSECONDS_PER_SECOND;
if (uptime <= 0) {
/* wanted_rpos <= 0 */
goto out_timer;
}
wanted_rpos = muldiv64(uptime, hda_bytes_per_second(st),
NANOSECONDS_PER_SECOND);
wanted_rpos &= -4; /* IMPORTANT! clip to frames */
if (wanted_rpos <= rpos) {
@ -286,12 +293,18 @@ static void hda_audio_output_timer(void *opaque)
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
int64_t buft_start = st->buft_start;
int64_t uptime = now - st->buft_start;
int64_t wpos = st->wpos;
int64_t rpos = st->rpos;
int64_t wanted_wpos;
int64_t wanted_wpos = hda_bytes_per_second(st) * (now - buft_start)
/ NANOSECONDS_PER_SECOND;
if (uptime <= 0) {
/* wanted_wpos <= 0 */
goto out_timer;
}
wanted_wpos = muldiv64(uptime, hda_bytes_per_second(st),
NANOSECONDS_PER_SECOND);
wanted_wpos &= -4; /* IMPORTANT! clip to frames */
if (wanted_wpos <= wpos) {