Subject: CVE-2024-41033: cachestat: do not flush stats in recency check

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

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

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

cachestat: do not flush stats in recency check

syzbot detects that cachestat() is flushing stats, which can sleep, in its
RCU read section (see [1]).  This is done in the workingset_test_recent()
step (which checks if the folio's eviction is recent).

Move the stat flushing step to before the RCU read section of cachestat,
and skip stat flushing during the recency check.

[1]: https://lore.kernel.org/cgroups/[email-masked]/

The Linux kernel CVE team has assigned CVE-2024-41033 to this issue.

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

	Issue introduced in 6.8 with commit b00684722262 and fixed in 6.9.10 with commit 1d1ba14e00d2
	Issue introduced in 6.8 with commit b00684722262 and fixed in 6.10 with commit 5a4d8944d6b1

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-2024-41033
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:
	include/linux/swap.h
	mm/filemap.c
	mm/workingset.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/1d1ba14e00d290b1ed616ed78c8c49bf897ce390
	https://git.kernel.org/stable/c/5a4d8944d6b1e1aaaa83ea42c116b520b4ed0394