CVE-2022-50773

/// Technical description

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

ALSA: mts64: fix possible null-ptr-defer in snd_mts64_interrupt

I got a null-ptr-defer error report when I do the following tests

on the qemu platform:

make defconfig and CONFIG_PARPORT=m, CONFIG_PARPORT_PC=m,

CONFIG_SND_MTS64=m

Then making test scripts:

cat>test_mod1.sh<<EOF

modprobe snd-mts64

modprobe snd-mts64

EOF

Executing the script, perhaps several times, we will get a null-ptr-defer

report, as follow:

syzkaller:~# ./test_mod.sh

snd_mts64: probe of snd_mts64.0 failed with error -5

modprobe: ERROR: could not insert 'snd_mts64': No such device

BUG: kernel NULL pointer dereference, address: 0000000000000000

#PF: supervisor write access in kernel mode

#PF: error_code(0x0002) - not-present page

PGD 0 P4D 0

Oops: 0002 [#1] PREEMPT SMP PTI

CPU: 0 PID: 205 Comm: modprobe Not tainted 6.1.0-rc8-00588-g76dcd734eca2 #6

Call Trace:

<IRQ>

snd_mts64_interrupt+0x24/0xa0 [snd_mts64]

parport_irq_handler+0x37/0x5

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References