# CVE-2022-48870: tty: fix possible null-ptr-defer in spk\_ttyio\_release

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-08-21 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.12

## Description

In the Linux kernel, the following vulnerability has been resolved: tty: fix possible null-ptr-defer in spk_ttyio_release Run the following tests on the qemu platform: syzkaller:~# modprobe speakup_audptr input: Speakup as /devices/virtual/input/input4 initialized device: /dev/synth, node (MAJOR 10, MINOR 125) speakup 3.1.6: initialized synth name on entry is: (null) synth probe spk_ttyio_initialise_ldisc failed because tty_kopen_exclusive returned failed (errno -16), then remove the module, we will get a null-ptr-defer problem, as follow: syzkaller:~# modprobe -r speakup_audptr releasing synth audptr BUG: kernel NULL pointer dereference, address: 0000000000000080 #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: 2 PID: 204 Comm: modprobe Not tainted 6.1.0-rc6-dirty #1 RIP: 0010:mutex_lock+0x14/0x30 Call Trace: <TASK> spk_ttyio_release+0x19/0x70 [speakup] synth_release.part.6+0xac/0xc0 [speakup] synth_remove+0x56/0x60 [speakup] __x64_sys_delete_module+0x156/0x250 ? fpregs_assert_state_consistent+0x1d/0x50 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd </TASK> Modules linked in: speakup_audptr(-) speakup Dumping ftrace buffer: in_synth->dev was not initialized during modprobe, so we add check for in_synth->dev to fix this bug.

## What to do

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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2da67bff29ab49caafb0766e8b8383b735ff796f
- https://git.kernel.org/stable/c/64152e05a4de3ebf59f1740a0985a6d5fba0c77b
- https://git.kernel.org/stable/c/5abbeebd8296c2301023b8dc4b5a6c0d5229b4f5

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