From 74e8593e7e51d6b11ae9c56a3f4e7bb714bac4ec Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Volker=20R=C3=BCmelin?= Date: Sun, 5 Nov 2023 18:25:51 +0100 Subject: [PATCH] hw/audio/hda-codec: fix multiplication overflow MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Volker Rümelin Message-Id: <20231105172552.8405-1-vr_qemu@t-online.de> Reviewed-by: Marc-André Lureau Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/audio/hda-codec.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/hw/audio/hda-codec.c b/hw/audio/hda-codec.c index b9ad1f4c39..f756e419bb 100644 --- a/hw/audio/hda-codec.c +++ b/hw/audio/hda-codec.c @@ -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) {