Subject: CVE-2024-42274: Revert "ALSA: firewire-lib: operate for period elapse event in process context"

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2024-42274 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.14 with commit 7ba5ca32fe6e and fixed in 5.15.165 with commit 7c07220cf634
	Issue introduced in 5.14 with commit 7ba5ca32fe6e and fixed in 6.1.104 with commit b239a37d68e8
	Issue introduced in 5.14 with commit 7ba5ca32fe6e and fixed in 6.6.45 with commit f5043e69aeb2
	Issue introduced in 5.14 with commit 7ba5ca32fe6e and fixed in 6.10.4 with commit 36c255db5a25
	Issue introduced in 5.14 with commit 7ba5ca32fe6e and fixed in 6.11 with commit 3dab73ab925a

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-42274
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	sound/firewire/amdtp-stream.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/7c07220cf634002f93a87ca2252a32766850f2d1
	https://git.kernel.org/stable/c/b239a37d68e8bc59f9516444da222841e3b13ba9
	https://git.kernel.org/stable/c/f5043e69aeb2786f32e84132817a007a6430aa7d
	https://git.kernel.org/stable/c/36c255db5a25edd42d1aca48e38b8e95ee5fd9ef
	https://git.kernel.org/stable/c/3dab73ab925a51ab05543b491bf17463a48ca323