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().

Fixes: 80bb50e2d459 ("ALSA: caiaq: take a reference on the USB device in create_card()")
Reported-by: syzbot+2afd7e71155c7e241560@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2afd7e71155c7e241560
Tested-by: syzbot+2afd7e71155c7e241560@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Link: https://patch.msgid.link/20260426001934.70813-1-kartikey406@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/caiaq/device.c b/sound/usb/caiaq/device.c
index 8af0c04041ee3edcb2df3dc78d5c0da863c91492..ad9f744b496bfb9a64668ec5b457250d5087563e 100644 (file)
--- a/sound/usb/caiaq/device.c
+++ b/sound/usb/caiaq/device.c
@@ -423,6 +423,7 @@ static int create_card(struct usb_device *usb_dev,
 
        cdev = caiaqdev(card);
        cdev->chip.dev = usb_get_dev(usb_dev);
+       card->private_free = card_free;
        cdev->chip.card = card;
        cdev->chip.usb_id = USB_ID(le16_to_cpu(usb_dev->descriptor.idVendor),
                                  le16_to_cpu(usb_dev->descriptor.idProduct));
@@ -511,7 +512,6 @@ static int init_card(struct snd_usb_caiaqdev *cdev)
        scnprintf(card->longname, sizeof(card->longname), "%s %s (%s)",
                       cdev->vendor_name, cdev->product_name, usbpath);
 
-       card->private_free = card_free;
        err = setup_card(cdev);
        if (err < 0)
                return err;