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ALSA: usb-audio: fix OOB write in snd_usbmidi_us122l_output()

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The snd_usbmidi_us122l_output() picks a count of 2 on anything slower
than high speed and never relates it to ep->max_transfer.  The URB
buffer holds exactly max_transfer bytes, so a device declaring a one
byte bulk endpoint takes two bytes from snd_rawmidi_transmit(), and the
memset that pads the rest computes 1 - 2 in int and wraps to SIZE_MAX.

Only 0x800e and 0x800f are pinned to nine bytes.  The US-122MKII at
0x0644:0x8021 falls to the default and takes usb_maxpacket(), which the
USB core only clamps downward.

The akai and novation output ops in this file were given the same guard
recently.  Do the same here.

Fixes: 030a07e441 ("ALSA: Add USB US122L driver")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Link: https://patch.msgid.link/20260901090409.1478573-1-sammiee5311@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
HyeongJun An 2026-09-01 18:04:09 +09:00 committed by Takashi Iwai
parent 9b110a9dce
commit e4637ce346
1 changed files with 2 additions and 0 deletions
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2
sound/usb/midi.c
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@ -971,6 +971,8 @@ static void snd_usbmidi_us122l_output(struct snd_usb_midi_out_endpoint *ep,
default:
count = 2;
}
if (ep->max_transfer < count)
return;
count = snd_rawmidi_transmit(ep->ports[0].substream,
urb->transfer_buffer,
count);