CVE-2026-23089

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

ALSA: usb-audio: Fix use-after-free in sndusbmixer_free()

When sndusbcreatemixer() fails, sndusbmixerfree() frees mixer->idelems but the controls already added to the card still reference the freed memory. Later when sndcard_register() runs, the OSS mixer layer calls their callbacks and hits a use-after-free read.

Call trace: getctlvalue+0x63f/0x820 sound/usb/mixer.c:411 getminmaxwithquirks.isra.0+0x240/0x1f40 sound/usb/mixer.c:1241 mixerctlfeatureinfo+0x26b/0x490 sound/usb/mixer.c:1381 sndmixerossbuildtest+0x174/0x3a0 sound/core/oss/mixeross.c:887 ... sndcardregister+0x4ed/0x6d0 sound/core/init.c:923 usbaudioprobe+0x5ef/0x2a90 sound/usb/card.c:1025

Fix by calling sndctlremove() for all mixer controls before freeing idelems. We save the next pointer first because sndctl_remove() frees the current element.