linux-cve-announce - CVE-2024-56560: slab: Fix too strict alignment check in create

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Message-ID: <2024122712-CVE-2024-56560-e044@gregkh>
Date: Fri, 27 Dec 2024 15:23:11 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-56560: slab: Fix too strict alignment check in create_cache()

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

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

slab: Fix too strict alignment check in create_cache()

On m68k, where the minimum alignment of unsigned long is 2 bytes:

    Kernel panic - not syncing: __kmem_cache_create_args: Failed to create slab 'io_kiocb'. Error -22
    CPU: 0 UID: 0 PID: 1 Comm: swapper Not tainted 6.12.0-atari-03776-g7eaa1f99261a #1783
    Stack from 0102fe5c:
	    0102fe5c 00514a2b 00514a2b ffffff00 00000001 0051f5ed 00425e78 00514a2b
	    0041eb74 ffffffea 00000310 0051f5ed ffffffea ffffffea 00601f60 00000044
	    0102ff20 000e7a68 0051ab8e 004383b8 0051f5ed ffffffea 000000b8 00000007
	    01020c00 00000000 000e77f0 0041e5f0 005f67c0 0051f5ed 000000b6 0102fef4
	    00000310 0102fef4 00000000 00000016 005f676c 0060a34c 00000010 00000004
	    00000038 0000009a 01000000 000000b8 005f668e 0102e000 00001372 0102ff88
    Call Trace: [<00425e78>] dump_stack+0xc/0x10
     [<0041eb74>] panic+0xd8/0x26c
     [<000e7a68>] __kmem_cache_create_args+0x278/0x2e8
     [<000e77f0>] __kmem_cache_create_args+0x0/0x2e8
     [<0041e5f0>] memset+0x0/0x8c
     [<005f67c0>] io_uring_init+0x54/0xd2

The minimal alignment of an integral type may differ from its size,
hence is not safe to assume that an arbitrary freeptr_t (which is
basically an unsigned long) is always aligned to 4 or 8 bytes.

As nothing seems to require the additional alignment, it is safe to fix
this by relaxing the check to the actual minimum alignment of freeptr_t.

The Linux kernel CVE team has assigned CVE-2024-56560 to this issue.


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

	Issue introduced in 6.12 with commit d345bd2e9834e2da505977e154a1c179c793b7b2 and fixed in 6.12.4 with commit 8b5aea5e5186733fa4e5aa4293b0a65a933f1a16
	Issue introduced in 6.12 with commit d345bd2e9834e2da505977e154a1c179c793b7b2 and fixed in 6.13-rc1 with commit 9008fe8fad8255edfdbecea32d7eb0485d939d0d

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-2024-56560
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/slab_common.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/8b5aea5e5186733fa4e5aa4293b0a65a933f1a16
	https://git.kernel.org/stable/c/9008fe8fad8255edfdbecea32d7eb0485d939d0d