CVE-2026-64428: gpio: sch: use raw_spinlock_t in the irq startup path

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

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

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

gpio: sch: use raw_spinlock_t in the irq startup path

sch_irq_unmask() enables the GPIO IRQ and then updates the controller
state through sch_irq_mask_unmask(), which takes sch->lock with
spin_lock_irqsave().  The callback can be reached from irq_startup()
while setting up a requested IRQ.  That path is not sleepable, but on
PREEMPT_RT a regular spinlock_t becomes a sleeping lock.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the request_threaded_irq() -> __setup_irq() ->
irq_startup() -> sch_irq_unmask() -> sch_irq_mask_unmask() carrier and
used the original spin_lock_irqsave(&sch->lock) edge.  Lockdep reported:

  BUG: sleeping function called from invalid context
  hardirqs last disabled at ... __setup_irq.constprop.0 ... [vuln_msv]
  sch_rt_spin_lock_irqsave+0x1c/0x30 [vuln_msv]
  sch_irq_mask_unmask.constprop.0+0x31/0x70 [vuln_msv]
  __setup_irq.constprop.0+0xd/0x30 [vuln_msv]

Convert the SCH controller lock to raw_spinlock_t.  The same lock is
also used by the GPIO direction and value callbacks, but those critical
sections only update MMIO-backed GPIO registers and do not 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.

The Linux kernel CVE team has assigned CVE-2026-64428 to this issue.


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

	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 5.15.212 with commit 3b1aa05ec27eeccc889ecaa3f2d9baa9f453e50d
	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 6.1.178 with commit 4f03a15cc73c83740fc355ee22b336492d17b4da
	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 6.6.145 with commit 7a550256d68bbdfa0903ab1c4595c04a6815493a
	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 6.12.97 with commit a235cec779bb39ec8f961a935b28a2ce278c6c64
	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 6.18.39 with commit 4508366ab7dd0c2917a51a9c2e23cc1b9d35157a
	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 7.1.4 with commit 41cad91a09d69e8fff4e936db29b1054b4e9f9f7
	Issue introduced in 5.13 with commit 7a81638485c1a62a87b4c391ecc9c651a4a9dc19 and fixed in 7.2-rc1 with commit 286533cb14a3c8a8bd39ff64ea2fc8e1aa0f638b

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-2026-64428
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-sch.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/3b1aa05ec27eeccc889ecaa3f2d9baa9f453e50d
	https://git.kernel.org/stable/c/4f03a15cc73c83740fc355ee22b336492d17b4da
	https://git.kernel.org/stable/c/7a550256d68bbdfa0903ab1c4595c04a6815493a
	https://git.kernel.org/stable/c/a235cec779bb39ec8f961a935b28a2ce278c6c64
	https://git.kernel.org/stable/c/4508366ab7dd0c2917a51a9c2e23cc1b9d35157a
	https://git.kernel.org/stable/c/41cad91a09d69e8fff4e936db29b1054b4e9f9f7
	https://git.kernel.org/stable/c/286533cb14a3c8a8bd39ff64ea2fc8e1aa0f638b