Affected: Linux

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

ALSA: caiaq: unregister the input device when probe fails

setup_card() registers the input device, whose name and phys point into struct snd_usb_caiaqdev, and then goes on to snd_card_register() and snd_usb_caiaq_control_init(). If either fails, snd_probe() calls snd_card_free(), which frees the device state but leaves the input device registered: card_free() only clears the pointer, and the input device is unregistered from snd_disconnect() alone. Reading its "uevent" attribute afterwards dereferences freed memory:

BUG: KASAN: slab-use-after-free in string+0x4a9/0x4f0 Read of size 1 at addr ffff8880208f5043 by task caiaq/4967 add_uevent_var+0x183/0x3a0 input_dev_uevent+0x162/0x900 dev_uevent+0x2f1/0x870 uevent_show+0x1ca/0x3a0 ...

Unregister the input device on the probe error path, as snd_disconnect() does. snd_usb_caiaq_input_disconnect() is a no-op when no input device was registered.

Reproduced with a raw-gadget Audio Kontrol 1 and a temporary hack that makes snd_usb_caiaq_control_init() fail.