[PATCH 6.6 067/105] ALSA: usb-audio: Fix NULL pointer deference in try_to_register_card

Greg Kroah-Hartman
2025-10-21T19:55:40Z

From: Jiaming Zhang <r772577952@gmail.com>

[ Upstream commit 28412b489b088fb88dff488305fd4e56bd47f6e4 ]

In try_to_register_card(), the return value of usb_ifnum_to_if() is
passed directly to usb_interface_claimed() without a NULL check, which
will lead to a NULL pointer dereference when creating an invalid
USB audio device. Fix this by adding a check to ensure the interface
pointer is valid before passing it to usb_interface_claimed().

Fixes: 39efc9c8a973 ("ALSA: usb-audio: Fix last interface check for registration")
Closes: https://lore.kernel.org/all/CANypQFYtQxHL5ghREs-BujZG413RPJGnO5TH=xjFBKpPts33tA@mail.gmail.com/
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/usb/card.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 7743ea983b1a8..9335bc20c56df 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -754,10 +754,16 @@ get_alias_quirk(struct usb_device *dev, unsigned int id)
*/
static int try_to_register_card(struct snd_usb_audio *chip, int ifnum)
{
+ struct usb_interface *iface;
+
if (check_delayed_register_option(chip) == ifnum ||
- chip->last_iface == ifnum ||
- usb_interface_claimed(usb_ifnum_to_if(chip->dev, chip->last_iface)))
+ chip->last_iface == ifnum)
+ return snd_card_register(chip->card);
+
+ iface = usb_ifnum_to_if(chip->dev, chip->last_iface);
+ if (iface && usb_interface_claimed(iface))
return snd_card_register(chip->card);
+
return 0;
}

--
2.51.0