Deadlock Affecting kernel-rt-debug-core package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-core package and not the kernel-rt-debug-core package as distributed by Centos. See How to fix? for Centos:8 relevant fixed versions and status.

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

Revert "ALSA: firewire-lib: operate for period elapse event in process context"

Commit 7ba5ca32fe6e ("ALSA: firewire-lib: operate for period elapse event in process context") removed the process context workqueue from amdtp_domain_stream_pcm_pointer() and update_pcm_pointers() to remove its overhead.

With RME Fireface 800, this lead to a regression since Kernels 5.14.0, causing an AB/BA deadlock competition for the substream lock with eventual system freeze under ALSA operation:

thread 0: * (lock A) acquire substream lock by snd_pcm_stream_lock_irq() in snd_pcm_status64() * (lock B) wait for tasklet to finish by calling tasklet_unlock_spin_wait() in tasklet_disable_in_atomic() in ohci_flush_iso_completions() of ohci.c

thread 1: * (lock B) enter tasklet * (lock A) attempt to acquire substream lock, waiting for it to be released: snd_pcm_stream_lock_irqsave() in snd_pcm_period_elapsed() in update_pcm_pointers() in process_ctx_payloads() in process_rx_packets() of amdtp-stream.c

? tasklet_unlock_spin_wait </NMI> <TASK> ohci_flush_iso_completions firewire_ohci amdtp_domain_stream_pcm_pointer snd_firewire_lib snd_pcm_update_hw_ptr0 snd_pcm snd_pcm_status64 snd_pcm

? native_queued_spin_lock_slowpath </NMI> <IRQ> _raw_spin_lock_irqsave snd_pcm_period_elapsed snd_pcm process_rx_packets snd_firewire_lib irq_target_callback snd_firewire_lib handle_it_packet firewire_ohci context_tasklet firewire_ohci

Restore the process context work queue to prevent deadlock AB/BA deadlock competition for ALSA substream lock of snd_pcm_stream_lock_irq() in snd_pcm_status64() and snd_pcm_stream_lock_irqsave() in snd_pcm_period_elapsed().

revert commit 7ba5ca32fe6e ("ALSA: firewire-lib: operate for period elapse event in process context")

Replace inline description to prevent future deadlock.

• https://access.redhat.com/security/cve/CVE-2024-42274
• https://git.kernel.org/stable/c/36c255db5a25edd42d1aca48e38b8e95ee5fd9ef
• https://git.kernel.org/stable/c/3dab73ab925a51ab05543b491bf17463a48ca323
• https://git.kernel.org/stable/c/b239a37d68e8bc59f9516444da222841e3b13ba9
• https://git.kernel.org/stable/c/f5043e69aeb2786f32e84132817a007a6430aa7d
• https://git.kernel.org/stable/c/7c07220cf634002f93a87ca2252a32766850f2d1