In the Linux kernel, the following vulnerability has been resolved: ALSA: caiaq: Decoupling ep1_in_urb in caiaq dev The epq_in_urb object belonging to the caiaq device is coupled within the struct snd_usb_caiaqdev

Overview

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

ALSA: caiaq: Decoupling ep1_in_urb in caiaq dev

The epq_in_urb object belonging to the caiaq device is coupled within the struct snd_usb_caiaqdev. After usb_submit_urb(epq_in_urb, GFP_KERNEL) executes successfully, epq_in_urb is successfully added to the urbp_list queue of the dummy HCD driver (userspace specifies dummy_hcd as the HCD layer driver for the caiaq USB device).

When init_card() calls snd_usb_caiaq_send_command() which subsequently fails due to a timeout, and proceeds to call snd_card_free() to release the card, the embedded ep1_in_urb object is also freed. When the dummy HCD driver detects that the URB has been unlinked, it returns the URB (by usb_hcd_giveback_urb()), which triggers [1].

Decouple the ep1_in_urb object from the struct snd_usb_caiaqdev and switch to using a pointer instead. Separately allocate and manage the memory for ep1_in_urb to prevent the release of the snd_card memory object from interfering with it.

midi_out_urb has the same issue as ep1_in_urb and is handled in the same way.

[1] BUG: KASAN: slab-use-after-free in usb_free_urb+0x24/0x120 drivers/usb/core/urb.c:96 Write of size 4 at addr ffff88803cee1050 by task ktimers/1/29 Call Trace: usb_free_urb+0x24/0x120 drivers/usb/core/urb.c:96 dummy_timer+0xaac/0x4d50 drivers/usb/gadget/udc/dummy_hcd.c:2019 __run_hrtimer kernel/time/hrtimer.c:2067 [inline] __hrtimer_run_queues+0x3eb/0xaf0 kernel/time/hrtimer.c:2124 hrtimer_run_softirq+0x1e1/0x2e0 kernel/time/hrtimer.c:2141

Allocated by task 36: snd_card_new+0x7b/0x110 sound/core/init.c:184 create_card sound/usb/caiaq/device.c:429 [inline] snd_probe+0x236/0x1af0 sound/usb/caiaq/device.c:544

Freed by task 36: snd_card_free_when_closed sound/core/init.c:630 [inline] snd_card_free+0x138/0x1d0 sound/core/init.c:662 snd_probe+0x162b/0x1af0 sound/usb/caiaq/device.c:553

Remediation

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