Commit b9c82691 authored Apr 10, 2026 by Berk Cem Goksel Committed by Takashi Iwai Apr 10, 2026

ALSA: 6fire: fix use-after-free on disconnect



In usb6fire_chip_abort(), the chip struct is allocated as the card's
private data (via snd_card_new with sizeof(struct sfire_chip)).  When
snd_card_free_when_closed() is called and no file handles are open, the
card and embedded chip are freed synchronously.  The subsequent
chip->card = NULL write then hits freed slab memory.

Call trace:
  usb6fire_chip_abort sound/usb/6fire/chip.c:59 [inline]
  usb6fire_chip_disconnect+0x348/0x358 sound/usb/6fire/chip.c:182
  usb_unbind_interface+0x1a8/0x88c drivers/usb/core/driver.c:458
  ...
  hub_event+0x1a04/0x4518 drivers/usb/core/hub.c:5953

Fix by moving the card lifecycle out of usb6fire_chip_abort() and into
usb6fire_chip_disconnect().  The card pointer is saved in a local
before any teardown, snd_card_disconnect() is called first to prevent
new opens, URBs are aborted while chip is still valid, and
snd_card_free_when_closed() is called last so chip is never accessed
after the card may be freed.

Fixes: a0810c3d ("ALSA: 6fire: Release resources at card release")
Cc: stable@vger.kernel.org
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Berk Cem Goksel <berkcgoksel@gmail.com>
Link: https://patch.msgid.link/20260410051341.1069716-1-berkcgoksel@gmail.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 07704bbf

sound/usb/6fire/chip.c

+12 −5

Original line number	Diff line number	Diff line
		@@ -53,11 +53,6 @@ static void usb6fire_chip_abort(struct sfire_chip *chip)
		usb6fire_comm_abort(chip);
		if (chip->control)
		usb6fire_control_abort(chip);
		if (chip->card) {
		snd_card_disconnect(chip->card);
		snd_card_free_when_closed(chip->card);
		chip->card = NULL;
		}
		}
		}

		@@ -168,6 +163,7 @@ static int usb6fire_chip_probe(struct usb_interface *intf,
		static void usb6fire_chip_disconnect(struct usb_interface *intf)
		{
		struct sfire_chip *chip;
		struct snd_card *card;

		chip = usb_get_intfdata(intf);
		if (chip) { /* if !chip, fw upload has been performed */
		@@ -178,8 +174,19 @@ static void usb6fire_chip_disconnect(struct usb_interface *intf)
		chips[chip->regidx] = NULL;
		}

		/*
		* Save card pointer before teardown.
		* snd_card_free_when_closed() may free card (and
		* the embedded chip) immediately, so it must be
		* called last and chip must not be accessed after.
		*/
		card = chip->card;
		chip->shutdown = true;
		if (card)
		snd_card_disconnect(card);
		usb6fire_chip_abort(chip);
		if (card)
		snd_card_free_when_closed(card);
		}
		}
		}