Subject: CVE-2024-46744: Squashfs: sanity check symbolic link size

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

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

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

Squashfs: sanity check symbolic link size

Syzkiller reports a "KMSAN: uninit-value in pick_link" bug.

This is caused by an uninitialised page, which is ultimately caused
by a corrupted symbolic link size read from disk.

The reason why the corrupted symlink size causes an uninitialised
page is due to the following sequence of events:

1. squashfs_read_inode() is called to read the symbolic
   link from disk.  This assigns the corrupted value
   3875536935 to inode->i_size.

2. Later squashfs_symlink_read_folio() is called, which assigns
   this corrupted value to the length variable, which being a
   signed int, overflows producing a negative number.

3. The following loop that fills in the page contents checks that
   the copied bytes is less than length, which being negative means
   the loop is skipped, producing an uninitialised page.

This patch adds a sanity check which checks that the symbolic
link size is not larger than expected.

--

V2: fix spelling mistake.

The Linux kernel CVE team has assigned CVE-2024-46744 to this issue.

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

	Fixed in 4.19.322 with commit f82cb7f24032
	Fixed in 5.4.284 with commit 1b9451ba6f21
	Fixed in 5.10.226 with commit 5c8906de98d0
	Fixed in 5.15.167 with commit 087f25b2d36a
	Fixed in 6.1.110 with commit fac5e82ab133
	Fixed in 6.6.51 with commit c3af7e460a52
	Fixed in 6.10.10 with commit ef4e249971eb
	Fixed in 6.11 with commit 810ee43d9cd2

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-2024-46744
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/squashfs/inode.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/f82cb7f24032ed023fc67d26ea9bf322d8431a90
	https://git.kernel.org/stable/c/1b9451ba6f21478a75288ea3e3fca4be35e2a438
	https://git.kernel.org/stable/c/5c8906de98d0d7ad42ff3edf2cb6cd7e0ea658c4
	https://git.kernel.org/stable/c/087f25b2d36adae19951114ffcbb7106ed405ebb
	https://git.kernel.org/stable/c/fac5e82ab1334fc8ed6ff7183702df634bd1d93d
	https://git.kernel.org/stable/c/c3af7e460a526007e4bed1ce3623274a1a6afe5e
	https://git.kernel.org/stable/c/ef4e249971eb77ec33d74c5c3de1e2576faf6c90
	https://git.kernel.org/stable/c/810ee43d9cd245d138a2733d87a24858a23f577d