linux-cve-announce - CVE-2022-50221: drm/fb-helper: Fix out-of-bounds access

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Message-ID: <2025061847-CVE-2022-50221-1b80@gregkh>
Date: Wed, 18 Jun 2025 13:04:46 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50221: drm/fb-helper: Fix out-of-bounds access

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

drm/fb-helper: Fix out-of-bounds access

Clip memory range to screen-buffer size to avoid out-of-bounds access
in fbdev deferred I/O's damage handling.

Fbdev's deferred I/O can only track pages. From the range of pages, the
damage handler computes the clipping rectangle for the display update.
If the fbdev screen buffer ends near the beginning of a page, that page
could contain more scanlines. The damage handler would then track these
non-existing scanlines as dirty and provoke an out-of-bounds access
during the screen update. Hence, clip the maximum memory range to the
size of the screen buffer.

While at it, rename the variables min/max to min_off/max_off in
drm_fb_helper_deferred_io(). This avoids confusion with the macros of
the same name.

The Linux kernel CVE team has assigned CVE-2022-50221 to this issue.

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

	Issue introduced in 5.18 with commit 67b723f5b74254d27962b1b59bddfee1584575ff and fixed in 5.19.2 with commit 9c49ac792c639dbec0728b513329a32461f72253
	Issue introduced in 5.18 with commit 67b723f5b74254d27962b1b59bddfee1584575ff and fixed in 6.0 with commit ae25885bdf59fde40726863c57fd20e4a0642183

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-2022-50221
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/gpu/drm/drm_fb_helper.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/9c49ac792c639dbec0728b513329a32461f72253
	https://git.kernel.org/stable/c/ae25885bdf59fde40726863c57fd20e4a0642183