Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

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.