usb: gadget: f_uac1_legacy: validate bRequest index in generic_{set,get}_cmd

Overview

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

usb: gadget: f_uac1_legacy: validate bRequest index in generic_{set,get}_cmd

generic_set_cmd() and generic_get_cmd() use the low nibble of ctrl->bRequest as an index into con->data[]:

u8 cmd = (ctrl->bRequest & 0x0F);  /* 0 .. 15 */
...
con->data[cmd] = value;            /* OOB when cmd >= 5 */

struct usb_audio_control (include/linux/usb/audio.h) declares data as a 5-element array, so indices 5 through 15 write (or read) up to 44 bytes past the end of the array on the heap.

A malicious USB host can craft a class-specific SET_CUR / GET_CUR request with an arbitrary bRequest value, triggering the out-of-bounds access from an IRQ completion handler with no further preconditions.

Add an ARRAY_SIZE() guard to both functions.

Affected

• Linux >= c47d7b09891abb4f8b222317c89c7469bed8db3a < 36f3f009049bc91e14dc856007932473318d12f8
• Linux >= c47d7b09891abb4f8b222317c89c7469bed8db3a < 8c611876c002d712ae5f246af5188432c708f79d
• Linux >= c47d7b09891abb4f8b222317c89c7469bed8db3a < 697cfe6e53b66cda196d6f8833b0ee97fefd0a8a
• Linux >= c47d7b09891abb4f8b222317c89c7469bed8db3a < 9062d50e75c24dc7911be05c9b1719b3b256af15
• Linux 2.6.31

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.