Affected: Linux

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

ALSA: ua101: reject mismatched capture/playback packet sizes

detect_usb_format() cross-checks bSubframeSize, bBitResolution and tSamFreq between the capture and playback interfaces, but never relates the two endpoints' wMaxPacketSize and bNrChannels. Each playback URB gets a buffer of ua->playback.max_packet_bytes, while the number of bytes written into it is derived from the capture stream: capture_urb_complete() computes frames from the received capture packet and capture.frame_bytes, and start_usb_playback() and playback_work() multiply that by playback.frame_bytes.

A device declaring a large capture wMaxPacketSize with few capture channels and a small playback wMaxPacketSize with many playback channels therefore memset()s and memcpy()s past the end of the playback buffer, in open() of the PCM node the driver registers during probe. usb_submit_urb() rejects the over-long iso_frame_desc[0].length with -EMSGSIZE, but only after the write.

Reject such descriptors at probe time. Genuine UA-101/UA-1000 hardware declares proportional packet sizes and is unaffected.

BUG: KASAN: slab-out-of-bounds in start_usb_playback (sound/usb/misc/ua101.c:586) Write of size 2048 at addr ffff8881098f3c00 by task exploit/5021 Call Trace: __asan_memset (mm/kasan/shadow.c:84) start_usb_playback (sound/usb/misc/ua101.c:586) playback_pcm_open (sound/usb/misc/ua101.c:679) snd_pcm_open_substream (sound/core/p…