Subject: CVE-2021-47042: drm/amd/display: Free local data after use

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

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

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

drm/amd/display: Free local data after use

Fixes the following memory leak in dc_link_construct():

unreferenced object 0xffffa03e81471400 (size 1024):
comm "amd_module_load", pid 2486, jiffies 4294946026 (age 10.544s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<000000000bdf5c4a>] kmem_cache_alloc_trace+0x30a/0x4a0
[<00000000e7c59f0e>] link_create+0xce/0xac0 [amdgpu]
[<000000002fb6c072>] dc_create+0x370/0x720 [amdgpu]
[<000000000094d1f3>] amdgpu_dm_init+0x18e/0x17a0 [amdgpu]
[<00000000bec048fd>] dm_hw_init+0x12/0x20 [amdgpu]
[<00000000a2bb7cf6>] amdgpu_device_init+0x1463/0x1e60 [amdgpu]
[<0000000032d3bb13>] amdgpu_driver_load_kms+0x5b/0x330 [amdgpu]
[<00000000a27834f9>] amdgpu_pci_probe+0x192/0x280 [amdgpu]
[<00000000fec7d291>] local_pci_probe+0x47/0xa0
[<0000000055dbbfa7>] pci_device_probe+0xe3/0x180
[<00000000815da970>] really_probe+0x1c4/0x4e0
[<00000000b4b6974b>] driver_probe_device+0x62/0x150
[<000000000f9ecc61>] device_driver_attach+0x58/0x60
[<000000000f65c843>] __driver_attach+0xd6/0x150
[<000000002f5e3683>] bus_for_each_dev+0x6a/0xc0
[<00000000a1cfc897>] driver_attach+0x1e/0x20

The Linux kernel CVE team has assigned CVE-2021-47042 to this issue.

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

	Issue introduced in 5.12 with commit 3a00c04212d1 and fixed in 5.12.4 with commit 296443139f89
	Issue introduced in 5.12 with commit 3a00c04212d1 and fixed in 5.13 with commit 616cf23b6cf4

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-2021-47042
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/core/dc_link.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/296443139f893b554dddd56a99ba8471ab5802d4
	https://git.kernel.org/stable/c/616cf23b6cf40ad6f03ffbddfa1b6c4eb68d8ae1