On 12/23/18 9:52 PM, Kővágó, Zoltán wrote:
> 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 <[email protected]>
> ---
> hw/usb/dev-audio.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/hw/usb/dev-audio.c b/hw/usb/dev-audio.c
> index 29475a2b70..45ffc3ebb3 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;
OK.
> };
>
> static void streambuf_init(struct streambuf *buf, uint32_t size,
> @@ -600,12 +600,14 @@ 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);
> + uint64_t free = buf->size - (buf->prod - buf->cons);
I'd use ssize_t here.
>
> if (free < USBAUDIO_PACKET_SIZE(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);
> @@ -614,7 +616,7 @@ 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;
> + uint64_t used = buf->prod - buf->cons;
> uint8_t *data;
>
> if (!used) {
Eventually here:
ssize_t used = buf->prod - buf->cons;
if (used <= 0) {
return NULL;
}
