CVE-2026-74468: gpio: pch: use raw_spinlock_t for the register lock

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

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

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

gpio: pch: use raw_spinlock_t for the register lock

pch_irq_type() is registered as the irq_chip .irq_set_type callback and
takes chip->spinlock with spin_lock_irqsave().  This callback is reached
from __setup_irq() -> __irq_set_trigger() -> chip->irq_set_type() while
the caller holds desc->lock, a raw_spinlock_t, with hardirqs disabled.
That context is not sleepable, but on PREEMPT_RT a regular spinlock_t is
an rtmutex-backed sleeping lock, so acquiring it there is invalid.

This was confirmed on a PREEMPT_RT kernel with lockdep
(PROVE_RAW_LOCK_NESTING and DEBUG_ATOMIC_SLEEP).  A grounded PoC mirrored
pch_irq_type()'s locking and drove it through the real genirq carrier
irq_set_irq_type() -> __irq_set_trigger() -> chip->irq_set_type(), i.e.
the same __irq_set_trigger() edge that __setup_irq() takes for a
requested IRQ.  With the original spin_lock_irqsave() edge lockdep
reported an invalid wait context, immediately followed by:

  BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
  in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 95, name: insmod
  hardirqs last disabled at (3784): _raw_spin_lock_irqsave+0x4f/0x60
   rt_spin_lock+0x3a/0x1c0
   repro_irq_set_type+0x64/0xa0 [pch_repro]
   __irq_set_trigger+0x69/0x140
   irq_set_irq_type+0x78/0xd0

Switching the mirrored lock to raw_spinlock_t made both splats go away.

Convert the register lock to raw_spinlock_t.  The same lock also
serializes the GPIO direction/value callbacks and the suspend/resume
register save/restore, but all of those critical sections only perform
MMIO register accesses (ioread32()/iowrite32()) and
irq_set_handler_locked(); none of them contain sleepable operations.
Keeping this register lock non-sleeping is therefore appropriate for the
irqchip callbacks and does not change the GPIO-side locking contract.

This is the same class of issue and fix as recently addressed for other
GPIO controllers, e.g. commit 286533cb14a3 ("gpio: sch: use raw_spinlock_t
in the irq startup path") and commit 90f0109019e6 ("gpio: eic-sprd: use
raw_spinlock_t in the irq startup path").

The Linux kernel CVE team has assigned CVE-2026-74468 to this issue.


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

	Issue introduced in 3.2 with commit 38eb18a6f92da886fc1af509d25e8f7a49e23d9a and fixed in 6.6.151 with commit 16da33cb36e663b6967112185e11d00ce8ff957c
	Issue introduced in 3.2 with commit 38eb18a6f92da886fc1af509d25e8f7a49e23d9a and fixed in 6.12.103 with commit ff050589a21967883bb55f6dba42568f8367ad4a
	Issue introduced in 3.2 with commit 38eb18a6f92da886fc1af509d25e8f7a49e23d9a and fixed in 6.18.44 with commit 466ab0c41d5f54f71cee60619d07c4abd0ffd2cd
	Issue introduced in 3.2 with commit 38eb18a6f92da886fc1af509d25e8f7a49e23d9a and fixed in 7.1.8 with commit c0a4ec89fc26e4b679b04f1002c503cb2529acdc
	Issue introduced in 3.2 with commit 38eb18a6f92da886fc1af509d25e8f7a49e23d9a and fixed in 7.2-rc6 with commit a02b8950d619123da64f69b70fe1dadef217dfe4

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-2026-74468
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:
	drivers/gpio/gpio-pch.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/16da33cb36e663b6967112185e11d00ce8ff957c
	https://git.kernel.org/stable/c/ff050589a21967883bb55f6dba42568f8367ad4a
	https://git.kernel.org/stable/c/466ab0c41d5f54f71cee60619d07c4abd0ffd2cd
	https://git.kernel.org/stable/c/c0a4ec89fc26e4b679b04f1002c503cb2529acdc
	https://git.kernel.org/stable/c/a02b8950d619123da64f69b70fe1dadef217dfe4