linux-cve-announce - CVE-2024-44947: fuse: Initialize beyond-EOF page contents before setting uptodate

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Message-ID: <2024090219-CVE-2024-44947-f49c@gregkh>
Date: Mon,  2 Sep 2024 19:36:20 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-44947: fuse: Initialize beyond-EOF page contents before setting uptodate

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

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

fuse: Initialize beyond-EOF page contents before setting uptodate

fuse_notify_store(), unlike fuse_do_readpage(), does not enable page
zeroing (because it can be used to change partial page contents).

So fuse_notify_store() must be more careful to fully initialize page
contents (including parts of the page that are beyond end-of-file)
before marking the page uptodate.

The current code can leave beyond-EOF page contents uninitialized, which
makes these uninitialized page contents visible to userspace via mmap().

This is an information leak, but only affects systems which do not
enable init-on-alloc (via CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y or the
corresponding kernel command line parameter).

The Linux kernel CVE team has assigned CVE-2024-44947 to this issue.

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

	Issue introduced in 2.6.36 with commit a1d75f258230 and fixed in 6.1.107 with commit 831433527773
	Issue introduced in 2.6.36 with commit a1d75f258230 and fixed in 6.6.48 with commit ac42e0f0eb66
	Issue introduced in 2.6.36 with commit a1d75f258230 and fixed in 6.10.7 with commit 18a067240817
	Issue introduced in 2.6.36 with commit a1d75f258230 and fixed in 6.11-rc4 with commit 3c0da3d163eb

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-2024-44947
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/fuse/dev.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/831433527773e665bdb635ab5783d0b95d1246f4
	https://git.kernel.org/stable/c/ac42e0f0eb66af966015ee33fd355bc6f5d80cd6
	https://git.kernel.org/stable/c/18a067240817bee8a9360539af5d79a4bf5398a5
	https://git.kernel.org/stable/c/3c0da3d163eb32f1f91891efaade027fa9b245b9