From e4637ce34607f1733a34a57294966d26b263e626 Mon Sep 17 00:00:00 2001 From: HyeongJun An Date: Tue, 1 Sep 2026 18:04:09 +0900 Subject: [PATCH] ALSA: usb-audio: fix OOB write in snd_usbmidi_us122l_output() 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: 030a07e44129 ("ALSA: Add USB US122L driver") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-5 Signed-off-by: HyeongJun An Link: https://patch.msgid.link/20260901090409.1478573-1-sammiee5311@gmail.com Signed-off-by: Takashi Iwai --- sound/usb/midi.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/usb/midi.c b/sound/usb/midi.c index 8a9bc37f0b6e..7e5b1b13360f 100644 --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -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);