linux-cve-announce - CVE-2022-49511: fbdev: defio: fix the pagelist corruption

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Message-ID: <2025022609-CVE-2022-49511-100a@gregkh>
Date: Wed, 26 Feb 2025 03:13:05 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49511: fbdev: defio: fix the pagelist corruption

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

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

fbdev: defio: fix the pagelist corruption

Easily hit the below list corruption:
==
list_add corruption. prev->next should be next (ffffffffc0ceb090), but
was ffffec604507edc8. (prev=ffffec604507edc8).
WARNING: CPU: 65 PID: 3959 at lib/list_debug.c:26
__list_add_valid+0x53/0x80
CPU: 65 PID: 3959 Comm: fbdev Tainted: G     U
RIP: 0010:__list_add_valid+0x53/0x80
Call Trace:
 <TASK>
 fb_deferred_io_mkwrite+0xea/0x150
 do_page_mkwrite+0x57/0xc0
 do_wp_page+0x278/0x2f0
 __handle_mm_fault+0xdc2/0x1590
 handle_mm_fault+0xdd/0x2c0
 do_user_addr_fault+0x1d3/0x650
 exc_page_fault+0x77/0x180
 ? asm_exc_page_fault+0x8/0x30
 asm_exc_page_fault+0x1e/0x30
RIP: 0033:0x7fd98fc8fad1
==

Figure out the race happens when one process is adding &page->lru into
the pagelist tail in fb_deferred_io_mkwrite(), another process is
re-initializing the same &page->lru in fb_deferred_io_fault(), which is
not protected by the lock.

This fix is to init all the page lists one time during initialization,
it not only fixes the list corruption, but also avoids INIT_LIST_HEAD()
redundantly.

V2: change "int i" to "unsigned int i" (Geert Uytterhoeven)

The Linux kernel CVE team has assigned CVE-2022-49511 to this issue.

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

	Issue introduced in 5.18 with commit 105a940416fc622406653b6fe54732897642dfbc and fixed in 5.18.3 with commit 6a9ae2fe887042f76fd3d334349e64e8ab3c55a2
	Issue introduced in 5.18 with commit 105a940416fc622406653b6fe54732897642dfbc and fixed in 5.19 with commit 856082f021a28221db2c32bd0531614a8382be67

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-2022-49511
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:
	drivers/video/fbdev/core/fb_defio.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/e79b2b2aadeffe1db54a6b569b9b621575c3eb07
	https://git.kernel.org/stable/c/6a9ae2fe887042f76fd3d334349e64e8ab3c55a2
	https://git.kernel.org/stable/c/856082f021a28221db2c32bd0531614a8382be67