CVE-2022-50773
Unknown Unknown - Not Provided
Null Pointer Dereference in Linux ALSA snd_mts64 Causes Kernel Panic

Publication date: 2025-12-24

Last updated on: 2025-12-24

Assigner: kernel.org

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+0x37/0x50 [parport] __handle_irq_event_percpu+0x39/0x190 handle_irq_event_percpu+0xa/0x30 handle_irq_event+0x2f/0x50 handle_edge_irq+0x99/0x1b0 __common_interrupt+0x5d/0x100 common_interrupt+0xa0/0xc0 </IRQ> <TASK> asm_common_interrupt+0x22/0x40 RIP: 0010:_raw_write_unlock_irqrestore+0x11/0x30 parport_claim+0xbd/0x230 [parport] snd_mts64_probe+0x14a/0x465 [snd_mts64] platform_probe+0x3f/0xa0 really_probe+0x129/0x2c0 __driver_probe_device+0x6d/0xc0 driver_probe_device+0x1a/0xa0 __device_attach_driver+0x7a/0xb0 bus_for_each_drv+0x62/0xb0 __device_attach+0xe4/0x180 bus_probe_device+0x82/0xa0 device_add+0x550/0x920 platform_device_add+0x106/0x220 snd_mts64_attach+0x2e/0x80 [snd_mts64] port_check+0x14/0x20 [parport] bus_for_each_dev+0x6e/0xc0 __parport_register_driver+0x7c/0xb0 [parport] snd_mts64_module_init+0x31/0x1000 [snd_mts64] do_one_initcall+0x3c/0x1f0 do_init_module+0x46/0x1c6 load_module+0x1d8d/0x1e10 __do_sys_finit_module+0xa2/0xf0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd </TASK> Kernel panic - not syncing: Fatal exception in interrupt Rebooting in 1 seconds.. The mts wa not initialized during interrupt, we add check for mts to fix this bug.
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Meta Information
Published
2025-12-24
Last Modified
2025-12-24
Generated
2026-05-07
AI Q&A
2025-12-24
EPSS Evaluated
2026-05-05
NVD
CVE-2022-50773
EUVD
EUVD-2022-55788
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a null pointer dereference in the ALSA mts64 driver in the Linux kernel. It occurs when the snd_mts64_interrupt function is called but the mts64 device was not properly initialized, leading to a null pointer dereference and a kernel panic. This happens when the snd-mts64 module is loaded multiple times without proper device initialization, causing the kernel to crash during interrupt handling.


How can this vulnerability impact me? :

This vulnerability can cause a kernel panic and system crash when the snd-mts64 module is loaded improperly or multiple times, leading to a denial of service. The system becomes unstable and may reboot unexpectedly, impacting availability and reliability.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by attempting to load the snd-mts64 kernel module multiple times and observing for null pointer dereference errors or kernel oops messages. For example, running a script that executes 'modprobe snd-mts64' repeatedly may trigger the error. The provided test script is: cat > test_mod1.sh <<EOF modprobe snd-mts64 modprobe snd-mts64 EOF Then execute: ./test_mod1.sh If the vulnerability is present, you may see errors such as 'snd_mts64: probe of snd_mts64.0 failed with error -5', 'modprobe: ERROR: could not insert 'snd_mts64': No such device', and kernel NULL pointer dereference oops messages.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves applying the fix that adds a check for the mts initialization during interrupt handling to prevent the null pointer dereference. Until the fix is applied, avoid loading the snd-mts64 module repeatedly or on systems where the hardware is not properly initialized to prevent kernel crashes. Monitoring for kernel oops messages related to snd_mts64 can help identify attempts to trigger the vulnerability.


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