CVE-2026-98946: drm/vc4: Disable the V3D interrupt across runtime suspend

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

drm/vc4: Disable the V3D interrupt across runtime suspend

vc4_irq_disable() masks the V3D interrupt sources and then calls
synchronize_irq() before the V3D is powered down. However, by itself,
this is not enough to quiesce the interrupt handler.

synchronize_irq() waits for handlers that have already set
IRQD_IRQ_INPROGRESS, and for irqchips reporting IRQCHIP_STATE_ACTIVE.
A GIC interrupt chip is able to mark an interrupt active as soon as a
CPU acknowledges it, so there these checks cover the whole dispatch path.
On RPi 0-3, however, the interrupt controller is ARMCTRL, which has no
active state. A CPU that has read the hwirq out of the pending register
but has not yet reached handle_level_irq() stays invisible to
synchronize_irq().

During a power transition, vc4_irq() may therefore run after the power
domain is off, where every V3D register read will return 0xdeadbeef.
0xdeadbeef has FLDONE, FRDONE and OUTOMEM set. This problem doesn't
trigger NULL pointer dereference issues only because the functions
vc4_irq_finish_bin_job() and vc4_irq_finish_render_job() return early
when there is no job pointer, but OUTOMEM is still able to schedule
vc4_overflow_mem_work() after vc4_irq_disable() has already cancelled it.

Therefore, fix the spurious interrupts by disabling the interrupt line
across the PM transition. To preserve the enable/disable balance, move
vc4_irq_install() and request the IRQ line disabled before the first
runtime resume.

The Linux kernel CVE team has assigned CVE-2026-98946 to this issue.


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

	Issue introduced in 6.1 with commit 9b6f461582e6b07e2ce93227a3e4661846e594ad and fixed in 7.2.11 with commit e81402c3d42041356cb7978510ebab997bc8d411
	Issue introduced in 6.1 with commit 9b6f461582e6b07e2ce93227a3e4661846e594ad and fixed in 7.3 with commit 6abc8e4dcfbc1d26a94c0ac037dfb3716f686b1f

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-2026-98946
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/gpu/drm/vc4/vc4_irq.c
	drivers/gpu/drm/vc4/vc4_v3d.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/e81402c3d42041356cb7978510ebab997bc8d411
	https://git.kernel.org/stable/c/6abc8e4dcfbc1d26a94c0ac037dfb3716f686b1f