Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT snd_pcm_group_lock_irq() acquires a spinlock_t and disables interrupts via spin_lock_irq(). This also implicitly disables the handling of softirqs such as TIMER_SOFTIRQ. On PREEMPT_RT softirqs are preemptible and spin_lock_irq() does not disable them. That means a timer can be invoked during spin_lock_irq() on the same CPU. Due to synchronisations reasons local_bh_disable() has a per-CPU lock named softirq_ctrl.lock which synchronizes individual softirq against each other. syz-bot managed to trigger a lockdep report where softirq_ctrl.lock is acquired in hrtimer_cancel() in addition to hrtimer_run_softirq(). This is a possible deadlock. The softirq_ctrl.lock can not be made part of spin_lock_irq() as this would lead to too much synchronisation against individual threads on the system. To avoid the possible deadlock, softirqs must be manually disabled before the lock is acquired. Disable softirqs before the lock is acquired on PREEMPT_RT.
References
- https://git.kernel.org/stable/c/3969b6193cb7a45aa5fb4ec68f215e9e7f93d39a
- https://git.kernel.org/stable/c/63ee96c7f47df239ee0a6e8108b6bfd8c98334ae
- https://git.kernel.org/stable/c/9fc4a3da9a0259a0500848b5d8657918efde176b
FAQ
What is CVE-2025-40142?
CVE-2025-40142 is a documented vulnerability. In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT snd_pcm_group_lock_irq() acquires a spinlock_t and dis...
How severe is CVE-2025-40142?
CVSS scoring is not yet available for CVE-2025-40142. Check NVD for updates.
Is there a patch for CVE-2025-40142?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.