Bug 2419925 (CVE-2025-40275)

Summary:	CVE-2025-40275 kernel: ALSA: usb-audio: Fix NULL pointer dereference in snd_usb_mixer_controls_badd
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	Keywords:	Security
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A null pointer dereference was found in the USB audio driver in the Linux kernel. For UAC3 devices, snd_usb_mixer_controls_badd() does not check if usb_ifnum_to_if() returns NULL before dereferencing the result. A malicious USB device with crafted descriptors can trigger this crash.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-12-08 07:09:20 UTC

In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: Fix NULL pointer dereference in snd_usb_mixer_controls_badd

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.

Comment 1 Jon Moroney 2025-12-08 19:11:02 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120717-CVE-2025-40275-021a@gregkh/T