CVE-2026-89753: mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec()

CVE-2026-89753: mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec()

[Greg Kroah-Hartman]

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

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

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

mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec()

I am seeing some rcu_tasks stalls in the Meta fleet during reclaim.

  INFO: rcu_tasks detected stalls on tasks:
	0000000088620d09: .. nvcsw: 6735/6735 holdout: 1 idle_cpu: -1/8
	task:GlobalCPUThread state:R  running task  pid:2552016 tgid:2524552
  Call Trace:
   shrink_lruvec
   mem_cgroup_iter
   shrink_node
   do_try_to_free_pages
   try_to_free_pages
   __alloc_frozen_pages_noprof
   alloc_pages_noprof
   pte_alloc_one
   __pte_alloc
   handle_mm_fault

Nothing promises direct reclaim returns in bounded time, and the scan loop
in shrink_lruvec() only calls cond_resched(), which is a no-op on
PREEMPTION kernels.  Involuntary preemption is not a Tasks-RCU quiescent
state, so the reclaiming task never reports one and becomes a holdout.

Upgrade it to cond_resched_tasks_rcu_qs(), which reports a quiescent state
even when cond_resched() does nothing.

PS: This has been discussed in [1]

The Linux kernel CVE team has assigned CVE-2026-89753 to this issue.


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

	Fixed in 6.12.109 with commit b5391676c61d94ffe3272dcf6723738b802f79e8
	Fixed in 6.18.50 with commit 3fd50239986302cb050d3649351bcec00fa9d5ab
	Fixed in 7.2.4 with commit cf3ba0911a1cf8680371ff113b90088edd01d2bb
	Fixed in 7.3-rc1 with commit 25f52e81216884a7444bf07a606691feb09a94e3

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-2026-89753
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:
	mm/vmscan.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/b5391676c61d94ffe3272dcf6723738b802f79e8
	https://git.kernel.org/stable/c/3fd50239986302cb050d3649351bcec00fa9d5ab
	https://git.kernel.org/stable/c/cf3ba0911a1cf8680371ff113b90088edd01d2bb
	https://git.kernel.org/stable/c/25f52e81216884a7444bf07a606691feb09a94e3