linux-cve-announce - CVE-2024-50177: drm/amd/display: fix a UBSAN warning in DML2.1

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Message-ID: <2024110807-CVE-2024-50177-73ee@gregkh>
Date: Fri,  8 Nov 2024 06:24:08 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50177: drm/amd/display: fix a UBSAN warning in DML2.1

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

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

drm/amd/display: fix a UBSAN warning in DML2.1

When programming phantom pipe, since cursor_width is explicity set to 0,
this causes calculation logic to trigger overflow for an unsigned int
triggering the kernel's UBSAN check as below:

[   40.962845] UBSAN: shift-out-of-bounds in /tmp/amd.EfpumTkO/amd/amdgpu/../display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.c:3312:34
[   40.962849] shift exponent 4294967170 is too large for 32-bit type 'unsigned int'
[   40.962852] CPU: 1 PID: 1670 Comm: gnome-shell Tainted: G        W  OE      6.5.0-41-generic #41~22.04.2-Ubuntu
[   40.962854] Hardware name: Gigabyte Technology Co., Ltd. X670E AORUS PRO X/X670E AORUS PRO X, BIOS F21 01/10/2024
[   40.962856] Call Trace:
[   40.962857]  <TASK>
[   40.962860]  dump_stack_lvl+0x48/0x70
[   40.962870]  dump_stack+0x10/0x20
[   40.962872]  __ubsan_handle_shift_out_of_bounds+0x1ac/0x360
[   40.962878]  calculate_cursor_req_attributes.cold+0x1b/0x28 [amdgpu]
[   40.963099]  dml_core_mode_support+0x6b91/0x16bc0 [amdgpu]
[   40.963327]  ? srso_alias_return_thunk+0x5/0x7f
[   40.963331]  ? CalculateWatermarksMALLUseAndDRAMSpeedChangeSupport+0x18b8/0x2790 [amdgpu]
[   40.963534]  ? srso_alias_return_thunk+0x5/0x7f
[   40.963536]  ? dml_core_mode_support+0xb3db/0x16bc0 [amdgpu]
[   40.963730]  dml2_core_calcs_mode_support_ex+0x2c/0x90 [amdgpu]
[   40.963906]  ? srso_alias_return_thunk+0x5/0x7f
[   40.963909]  ? dml2_core_calcs_mode_support_ex+0x2c/0x90 [amdgpu]
[   40.964078]  core_dcn4_mode_support+0x72/0xbf0 [amdgpu]
[   40.964247]  dml2_top_optimization_perform_optimization_phase+0x1d3/0x2a0 [amdgpu]
[   40.964420]  dml2_build_mode_programming+0x23d/0x750 [amdgpu]
[   40.964587]  dml21_validate+0x274/0x770 [amdgpu]
[   40.964761]  ? srso_alias_return_thunk+0x5/0x7f
[   40.964763]  ? resource_append_dpp_pipes_for_plane_composition+0x27c/0x3b0 [amdgpu]
[   40.964942]  dml2_validate+0x504/0x750 [amdgpu]
[   40.965117]  ? dml21_copy+0x95/0xb0 [amdgpu]
[   40.965291]  ? srso_alias_return_thunk+0x5/0x7f
[   40.965295]  dcn401_validate_bandwidth+0x4e/0x70 [amdgpu]
[   40.965491]  update_planes_and_stream_state+0x38d/0x5c0 [amdgpu]
[   40.965672]  update_planes_and_stream_v3+0x52/0x1e0 [amdgpu]
[   40.965845]  ? srso_alias_return_thunk+0x5/0x7f
[   40.965849]  dc_update_planes_and_stream+0x71/0xb0 [amdgpu]

Fix this by adding a guard for checking cursor width before triggering
the size calculation.

The Linux kernel CVE team has assigned CVE-2024-50177 to this issue.


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

	Fixed in 6.11.3 with commit 27bc3da5eae5
	Fixed in 6.12-rc1 with commit eaf3adb8faab

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-2024-50177
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/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4_calcs.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/27bc3da5eae57e3af8f5648b4498ffde48781434
	https://git.kernel.org/stable/c/eaf3adb8faab611ba57594fa915893fc93a7788c