Subject: CVE-2024-43901: drm/amd/display: Fix NULL pointer dereference for DTN log in DCN401

From: Greg Kroah-Hartman <[email-masked]>

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

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

drm/amd/display: Fix NULL pointer dereference for DTN log in DCN401

When users run the command:

cat /sys/kernel/debug/dri/0/amdgpu_dm_dtn_log

The following NULL pointer dereference happens:

[  +0.000003] BUG: kernel NULL pointer dereference, address: NULL
[  +0.000005] #PF: supervisor instruction fetch in kernel mode
[  +0.000002] #PF: error_code(0x0010) - not-present page
[  +0.000002] PGD 0 P4D 0
[  +0.000004] Oops: 0010 [#1] PREEMPT SMP NOPTI
[  +0.000003] RIP: 0010:0x0
[  +0.000008] Code: Unable to access opcode bytes at 0xffffffffffffffd6.
[...]
[  +0.000002] PKRU: 55555554
[  +0.000002] Call Trace:
[  +0.000002]  <TASK>
[  +0.000003]  ? show_regs+0x65/0x70
[  +0.000006]  ? __die+0x24/0x70
[  +0.000004]  ? page_fault_oops+0x160/0x470
[  +0.000006]  ? do_user_addr_fault+0x2b5/0x690
[  +0.000003]  ? prb_read_valid+0x1c/0x30
[  +0.000005]  ? exc_page_fault+0x8c/0x1a0
[  +0.000005]  ? asm_exc_page_fault+0x27/0x30
[  +0.000012]  dcn10_log_color_state+0xf9/0x510 [amdgpu]
[  +0.000306]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000003]  ? vsnprintf+0x2fb/0x600
[  +0.000009]  dcn10_log_hw_state+0xfd0/0xfe0 [amdgpu]
[  +0.000218]  ? __mod_memcg_lruvec_state+0xe8/0x170
[  +0.000008]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000002]  ? debug_smp_processor_id+0x17/0x20
[  +0.000003]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000002]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000002]  ? set_ptes.isra.0+0x2b/0x90
[  +0.000004]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000002]  ? _raw_spin_unlock+0x19/0x40
[  +0.000004]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000002]  ? do_anonymous_page+0x337/0x700
[  +0.000004]  dtn_log_read+0x82/0x120 [amdgpu]
[  +0.000207]  full_proxy_read+0x66/0x90
[  +0.000007]  vfs_read+0xb0/0x340
[  +0.000005]  ? __count_memcg_events+0x79/0xe0
[  +0.000002]  ? srso_alias_return_thunk+0x5/0xfbef5
[  +0.000003]  ? count_memcg_events.constprop.0+0x1e/0x40
[  +0.000003]  ? handle_mm_fault+0xb2/0x370
[  +0.000003]  ksys_read+0x6b/0xf0
[  +0.000004]  __x64_sys_read+0x19/0x20
[  +0.000003]  do_syscall_64+0x60/0x130
[  +0.000004]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
[  +0.000003] RIP: 0033:0x7fdf32f147e2
[...]

This error happens when the color log tries to read the gamut remap
information from DCN401 which is not initialized in the dcn401_dpp_funcs
which leads to a null pointer dereference. This commit addresses this
issue by adding a proper guard to access the gamut_remap callback in
case the specific ASIC did not implement this function.

The Linux kernel CVE team has assigned CVE-2024-43901 to this issue.

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

	Fixed in 6.10.5 with commit 1e68b7ce6bc6
	Fixed in 6.11 with commit 5af757124792

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-2024-43901
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/hwss/dcn10/dcn10_hwseq.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/1e68b7ce6bc6073579fe8713ec6b85aa9cd2e351
	https://git.kernel.org/stable/c/5af757124792817f8eb1bd0c80ad60fab519586b