Re: [PATCH v3] ALSA: usb-audio: Fix NULL pointer dereference in snd_usb_mixer_controls_badd

[Takashi Iwai]

On Tue, 11 Nov 2025 16:37:54 +0100,
Haein Lee wrote:
> 
> In snd_usb_create_streams(), for UAC version 3 devices, the Interface
> Association Descriptor (IAD) is retrieved via usb_ifnum_to_if(). If this
> call fails, a fallback routine attempts to obtain the IAD from the next
> interface and sets a BADD profile. However, snd_usb_mixer_controls_badd()
> assumes that the IAD retrieved from usb_ifnum_to_if() is always valid,
> without performing a NULL check. This can lead to a NULL pointer
> dereference when usb_ifnum_to_if() fails to find the interface descriptor.
> 
> This patch adds a NULL pointer check after calling usb_ifnum_to_if() in
> snd_usb_mixer_controls_badd() to prevent the dereference.
> 
> This issue was discovered by syzkaller, which triggered the bug by sending
> a crafted USB device descriptor.
> 
> Signed-off-by: Haein Lee <lhi0729@xxxxxxxxxxx>

Applied now.  Thanks.


Takashi