linux-cve-announce - CVE-2024-56616: drm/dp_mst: Fix MST sideband message body length check

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Message-ID: <2024122708-CVE-2024-56616-ae89@gregkh>
Date: Fri, 27 Dec 2024 15:51:23 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-56616: drm/dp_mst: Fix MST sideband message body length check

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

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

drm/dp_mst: Fix MST sideband message body length check

Fix the MST sideband message body length check, which must be at least 1
byte accounting for the message body CRC (aka message data CRC) at the
end of the message.

This fixes a case where an MST branch device returns a header with a
correct header CRC (indicating a correctly received body length), with
the body length being incorrectly set to 0. This will later lead to a
memory corruption in drm_dp_sideband_append_payload() and the following
errors in dmesg:

   UBSAN: array-index-out-of-bounds in drivers/gpu/drm/display/drm_dp_mst_topology.c:786:25
   index -1 is out of range for type 'u8 [48]'
   Call Trace:
    drm_dp_sideband_append_payload+0x33d/0x350 [drm_display_helper]
    drm_dp_get_one_sb_msg+0x3ce/0x5f0 [drm_display_helper]
    drm_dp_mst_hpd_irq_handle_event+0xc8/0x1580 [drm_display_helper]

   memcpy: detected field-spanning write (size 18446744073709551615) of single field "&msg->msg[msg->curlen]" at drivers/gpu/drm/display/drm_dp_mst_topology.c:791 (size 256)
   Call Trace:
    drm_dp_sideband_append_payload+0x324/0x350 [drm_display_helper]
    drm_dp_get_one_sb_msg+0x3ce/0x5f0 [drm_display_helper]
    drm_dp_mst_hpd_irq_handle_event+0xc8/0x1580 [drm_display_helper]

The Linux kernel CVE team has assigned CVE-2024-56616 to this issue.


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

	Fixed in 6.1.120 with commit 780fa184d4dc38ad6c4fded345ab8f9be7a63e96
	Fixed in 6.6.66 with commit c58947a8d4a500902597ee1dbadf0518d7ff8801
	Fixed in 6.12.5 with commit 1fc1f32c4a3421b9d803f18ec3ef49db2fb5d5ef
	Fixed in 6.13-rc2 with commit bd2fccac61b40eaf08d9546acc9fef958bfe4763

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-2024-56616
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/display/drm_dp_mst_topology.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/780fa184d4dc38ad6c4fded345ab8f9be7a63e96
	https://git.kernel.org/stable/c/c58947a8d4a500902597ee1dbadf0518d7ff8801
	https://git.kernel.org/stable/c/1fc1f32c4a3421b9d803f18ec3ef49db2fb5d5ef
	https://git.kernel.org/stable/c/bd2fccac61b40eaf08d9546acc9fef958bfe4763