Subject: CVE-2021-47142: drm/amdgpu: Fix a use-after-free

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

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

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

drm/amdgpu: Fix a use-after-free

looks like we forget to set ttm->sg to NULL.
Hit panic below

[ 1235.844104] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b7b4b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI
[ 1235.989074] Call Trace:
[ 1235.991751]  sg_free_table+0x17/0x20
[ 1235.995667]  amdgpu_ttm_backend_unbind.cold+0x4d/0xf7 [amdgpu]
[ 1236.002288]  amdgpu_ttm_backend_destroy+0x29/0x130 [amdgpu]
[ 1236.008464]  ttm_tt_destroy+0x1e/0x30 [ttm]
[ 1236.013066]  ttm_bo_cleanup_memtype_use+0x51/0xa0 [ttm]
[ 1236.018783]  ttm_bo_release+0x262/0xa50 [ttm]
[ 1236.023547]  ttm_bo_put+0x82/0xd0 [ttm]
[ 1236.027766]  amdgpu_bo_unref+0x26/0x50 [amdgpu]
[ 1236.032809]  amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x7aa/0xd90 [amdgpu]
[ 1236.040400]  kfd_ioctl_alloc_memory_of_gpu+0xe2/0x330 [amdgpu]
[ 1236.046912]  kfd_ioctl+0x463/0x690 [amdgpu]

The Linux kernel CVE team has assigned CVE-2021-47142 to this issue.

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

	Fixed in 4.4.271 with commit 0707c3fea810
	Fixed in 4.9.271 with commit 3293cf3513d6
	Fixed in 4.14.235 with commit 952ab3f9f48e
	Fixed in 4.19.193 with commit a849e218556f
	Fixed in 5.4.124 with commit 7398c2aab4da
	Fixed in 5.10.42 with commit f98cdf084405
	Fixed in 5.12.9 with commit d4ea141fd4b4
	Fixed in 5.13 with commit 1e5c37385097

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-2021-47142
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/amdgpu/amdgpu_ttm.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/0707c3fea8102d211631ba515ef2159707561b0d
	https://git.kernel.org/stable/c/3293cf3513d69f00c14d43e2020826d45ea0e46a
	https://git.kernel.org/stable/c/952ab3f9f48eb0e8050596d41951cf516be6b122
	https://git.kernel.org/stable/c/a849e218556f932576c0fb1c5a88714b61709a17
	https://git.kernel.org/stable/c/7398c2aab4da960761ec182d04d6d5abbb4a226e
	https://git.kernel.org/stable/c/f98cdf084405333ee2f5be548a91b2d168e49276
	https://git.kernel.org/stable/c/d4ea141fd4b40636a8326df5a377d9c5cf9b3faa
	https://git.kernel.org/stable/c/1e5c37385097c35911b0f8a0c67ffd10ee1af9a2