linux-cve-announce - CVE-2022-50036: drm/sun4i: dsi: Prevent underflow when computing packet sizes

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Message-ID: <2025061840-CVE-2022-50036-7fdc@gregkh>
Date: Wed, 18 Jun 2025 13:01:41 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50036: drm/sun4i: dsi: Prevent underflow when computing packet sizes

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

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

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

drm/sun4i: dsi: Prevent underflow when computing packet sizes

Currently, the packet overhead is subtracted using unsigned arithmetic.
With a short sync pulse, this could underflow and wrap around to near
the maximal u16 value. Fix this by using signed subtraction. The call to
max() will correctly handle any negative numbers that are produced.

Apply the same fix to the other timings, even though those subtractions
are less likely to underflow.

The Linux kernel CVE team has assigned CVE-2022-50036 to this issue.


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

	Issue introduced in 4.18 with commit 133add5b5ad42b7bb5fcd59d681aef6475d08600 and fixed in 5.10.138 with commit a1e7908f78f5a7f53f8cd83c7dcdfec974c95f26
	Issue introduced in 4.18 with commit 133add5b5ad42b7bb5fcd59d681aef6475d08600 and fixed in 5.15.63 with commit 98e28de472ef248352f04f87e29e634ebb0ec240
	Issue introduced in 4.18 with commit 133add5b5ad42b7bb5fcd59d681aef6475d08600 and fixed in 5.19.4 with commit fb837f5b83461624e525727a8f4add14b201147e
	Issue introduced in 4.18 with commit 133add5b5ad42b7bb5fcd59d681aef6475d08600 and fixed in 6.0 with commit 82a1356a933d8443139f8886f11b63c974a09a67

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-2022-50036
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/sun4i/sun6i_mipi_dsi.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/a1e7908f78f5a7f53f8cd83c7dcdfec974c95f26
	https://git.kernel.org/stable/c/98e28de472ef248352f04f87e29e634ebb0ec240
	https://git.kernel.org/stable/c/fb837f5b83461624e525727a8f4add14b201147e
	https://git.kernel.org/stable/c/82a1356a933d8443139f8886f11b63c974a09a67