In the Linux kernel, the following vulnerability has been resolved:
ALSA: caiaq: fix usb_dev refcount leak on probe failure
create_card() takes a reference on the USB device with usb_get_dev()
and stores the matching usb_put_dev() in card_free(), which is
installed as the snd_card's ->private_free destructor.
However, ->private_free is only assigned near the end of init_card(),
after several failure points (usb_set_interface(), EP type checks,
usb_submit_urb(), the EP1_CMD_GET_DEVICE_INFO exchange, and its
timeout). When any of those fail, init_card() returns an error to
snd_probe(), which calls snd_card_free(card). Because ->private_free
is still NULL, card_free() never runs, the usb_get_dev() reference
is not dropped, and the struct usb_device leaks along with its
descriptor allocations and device_private.
syzbot reproduces this with a malformed UAC3 device whose only valid
altsetting is 0; init_card()'s usb_set_interface(usb_dev, 0, 1) call
fails with -EIO and triggers the leak.
Move the ->private_free assignment into create_card(), immediately
after usb_get_dev(), so that every error path reaching snd_card_free()
balances the reference. card_free()'s callees (snd_usb_caiaq_input_free,
free_urbs, kfree) already tolerate the partially-initialized state
because the chip private area is zero-initialized by snd_card_new().