linux-cve-announce - CVE-2022-49655: fscache: Fix invalidation/lookup race

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Message-ID: <2025022621-CVE-2022-49655-0370@gregkh>
Date: Wed, 26 Feb 2025 03:23:38 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49655: fscache: Fix invalidation/lookup race

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

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

fscache: Fix invalidation/lookup race

If an NFS file is opened for writing and closed, fscache_invalidate() will
be asked to invalidate the file - however, if the cookie is in the
LOOKING_UP state (or the CREATING state), then request to invalidate
doesn't get recorded for fscache_cookie_state_machine() to do something
with.

Fix this by making __fscache_invalidate() set a flag if it sees the cookie
is in the LOOKING_UP state to indicate that we need to go to invalidation.
Note that this requires a count on the n_accesses counter for the state
machine, which that will release when it's done.

fscache_cookie_state_machine() then shifts to the INVALIDATING state if it
sees the flag.

Without this, an nfs file can get corrupted if it gets modified locally and
then read locally as the cache contents may not get updated.

The Linux kernel CVE team has assigned CVE-2022-49655 to this issue.

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

	Issue introduced in 5.17 with commit d24af13e2e2358a602740c7817ea90da43d3e740 and fixed in 5.18.11 with commit b1ae9f617f8a5c848d9205b8e228c6f0d1af754b
	Issue introduced in 5.17 with commit d24af13e2e2358a602740c7817ea90da43d3e740 and fixed in 5.19 with commit 85e4ea1049c70fb99de5c6057e835d151fb647da

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-2022-49655
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:
	fs/fscache/cookie.c
	include/linux/fscache.h

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/b1ae9f617f8a5c848d9205b8e228c6f0d1af754b
	https://git.kernel.org/stable/c/85e4ea1049c70fb99de5c6057e835d151fb647da