Re: [PATCH] ALSA: firewire: isight: bound the sample count to the packet payload

[Takashi Iwai]

On Sun, 21 Jun 2026 17:09:07 +0200,
Maoyi Xie wrote:
> 
> isight_packet() takes the frame count from the device iso packet and
> checks it only against the device claimed iso length.
> 
> 	count = be32_to_cpu(payload->sample_count);
> 	if (likely(count <= (length - 16) / 4))
> 		isight_samples(isight, payload->samples, count);
> 
> length is the iso header data_length. It can be up to 0xffff. So the
> gate allows a count up to about 16379. isight_samples() then copies
> count frames out of payload->samples into the PCM DMA buffer.
> 
> payload->samples holds only 2 * MAX_FRAMES_PER_PACKET values. The
> device multiplexes two samples per frame. A count past
> MAX_FRAMES_PER_PACKET reads past the payload. A count past the buffer
> size writes past runtime->dma_area. The smallest PCM buffer is larger
> than MAX_FRAMES_PER_PACKET. Bounding the count to MAX_FRAMES_PER_PACKET
> keeps both the read and the write in range.
> 
> A malicious or faulty Apple iSight on the FireWire bus reaches this
> during a normal capture.
> 
> Add the MAX_FRAMES_PER_PACKET bound to the gate.
> 
> Fixes: 3a691b28a0ca ("ALSA: add Apple iSight microphone driver")
> Suggested-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Maoyi Xie <maoyixie.tju@xxxxxxxxx>

Thanks, applied now.


Takashi