Re: [PATCH] ALSA: caiaq: fix usb_dev refcount leak on probe failure

[Takashi Iwai]

On Sun, 26 Apr 2026 02:19:34 +0200,
Deepanshu Kartikey wrote:
> 
> 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().
> 
> Reported-by: syzbot+2afd7e71155c7e241560@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=2afd7e71155c7e241560
> Tested-by: syzbot+2afd7e71155c7e241560@xxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>

Applied now.  Thanks.


Takashi