linux-cve-announce - CVE-2025-21691: cachestat: fix page cache statistics permission checking

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Message-ID: <2025021055-CVE-2025-21691-2bd2@gregkh>
Date: Mon, 10 Feb 2025 16:58:59 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21691: cachestat: fix page cache statistics permission checking

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

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

cachestat: fix page cache statistics permission checking

When the 'cachestat()' system call was added in commit cf264e1329fb
("cachestat: implement cachestat syscall"), it was meant to be a much
more convenient (and performant) version of mincore() that didn't need
mapping things into the user virtual address space in order to work.

But it ended up missing the "check for writability or ownership" fix for
mincore(), done in commit 134fca9063ad ("mm/mincore.c: make mincore()
more conservative").

This just adds equivalent logic to 'cachestat()', modified for the file
context (rather than vma).

The Linux kernel CVE team has assigned CVE-2025-21691 to this issue.


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

	Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.6.75 with commit 7d6405c13b0d8a8367cd8df63f118b619a3f0dd2
	Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.12.12 with commit 780ab8329672464984cf1344bd5c3993af0226c7
	Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.13.1 with commit 97153a05077f618f7471f50a78158602badccb30
	Issue introduced in 6.5 with commit cf264e1329fb0307e044f7675849f9f38b44c11a and fixed in 6.14-rc1 with commit 5f537664e705b0bf8b7e329861f20128534f6a83

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-2025-21691
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/filemap.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/7d6405c13b0d8a8367cd8df63f118b619a3f0dd2
	https://git.kernel.org/stable/c/780ab8329672464984cf1344bd5c3993af0226c7
	https://git.kernel.org/stable/c/97153a05077f618f7471f50a78158602badccb30
	https://git.kernel.org/stable/c/5f537664e705b0bf8b7e329861f20128534f6a83