In the Linux kernel, the following vulnerability has been resolved:
ALSA: control: Don’t add invalid kcontrols to LED layer
The kcontrol LED state layer tries to track the all associated
kcontrol elements with naive assumptions that they are readable.
But one can create a write-only element that has no get callback (even
a user element can do it), and this may lead to a NULL dereference at
the call chain of snd_ctl_led_notify(), as found by syzkaller.
For avoiding the Oops, add a sanity check of the kcontrol’s info and
get callbacks, and just skip the invalid kcontrols before assigning
the kctl to the LED layer.
