With stereo playback, they need about 375 minutes of continuous audio playback to overflow, which is usually not a problem (as stopping and later resuming playback resets the counters). But with 7.1 audio, they only need about 95 minutes to overflow.
After the overflow, the buf->prod % USBAUDIO_PACKET_SIZE(channels) assertion no longer holds true, which will result in overflowing the buffer. With 64 bit variables, it would take about 762000 years to overflow. Signed-off-by: Kővágó, Zoltán <dirty.ice...@gmail.com> --- hw/usb/dev-audio.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/hw/usb/dev-audio.c b/hw/usb/dev-audio.c index f7406da5a4..82bc6eb88f 100644 --- a/hw/usb/dev-audio.c +++ b/hw/usb/dev-audio.c @@ -577,9 +577,9 @@ static const USBDesc desc_audio_multi = { struct streambuf { uint8_t *data; - uint32_t size; - uint32_t prod; - uint32_t cons; + size_t size; + uint64_t prod; + uint64_t cons; }; static void streambuf_init(struct streambuf *buf, uint32_t size, @@ -600,7 +600,7 @@ static void streambuf_fini(struct streambuf *buf) static int streambuf_put(struct streambuf *buf, USBPacket *p, uint32_t channels) { - uint32_t free = buf->size - (buf->prod - buf->cons); + int64_t free = buf->size - (buf->prod - buf->cons); if (free < USBAUDIO_PACKET_SIZE(channels)) { return 0; @@ -609,6 +609,8 @@ static int streambuf_put(struct streambuf *buf, USBPacket *p, uint32_t channels) return 0; } + /* can happen if prod overflows */ + assert(buf->prod % USBAUDIO_PACKET_SIZE(channels) == 0); usb_packet_copy(p, buf->data + (buf->prod % buf->size), USBAUDIO_PACKET_SIZE(channels)); buf->prod += USBAUDIO_PACKET_SIZE(channels); @@ -617,10 +619,10 @@ static int streambuf_put(struct streambuf *buf, USBPacket *p, uint32_t channels) static uint8_t *streambuf_get(struct streambuf *buf, size_t *len) { - uint32_t used = buf->prod - buf->cons; + int64_t used = buf->prod - buf->cons; uint8_t *data; - if (!used) { + if (used <= 0) { *len = 0; return NULL; } -- 2.20.1