Subject: CVE-2021-47421: drm/amdgpu: handle the case of pci_channel_io_frozen only in amdgpu_pci_resume

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

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

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

drm/amdgpu: handle the case of pci_channel_io_frozen only in amdgpu_pci_resume

In current code, when a PCI error state pci_channel_io_normal is detectd,
it will report PCI_ERS_RESULT_CAN_RECOVER status to PCI driver, and PCI
driver will continue the execution of PCI resume callback report_resume by
pci_walk_bridge, and the callback will go into amdgpu_pci_resume
finally, where write lock is releasd unconditionally without acquiring
such lock first. In this case, a deadlock will happen when other threads
start to acquire the read lock.

To fix this, add a member in amdgpu_device strucutre to cache
pci_channel_state, and only continue the execution in amdgpu_pci_resume
when it's pci_channel_io_frozen.

The Linux kernel CVE team has assigned CVE-2021-47421 to this issue.

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

	Issue introduced in 5.10 with commit c9a6b82f45e2 and fixed in 5.14.12 with commit 72e9a1bf9b72
	Issue introduced in 5.10 with commit c9a6b82f45e2 and fixed in 5.15 with commit 248b061689a4

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-2021-47421
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.h
	drivers/gpu/drm/amd/amdgpu/amdgpu_device.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/72e9a1bf9b722628c28092e0c2cd8717edd201dc
	https://git.kernel.org/stable/c/248b061689a40f4fed05252ee2c89f87cf26d7d8