Subject: CVE-2021-47228: x86/ioremap: Map EFI-reserved memory as encrypted for SEV

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

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

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

x86/ioremap: Map EFI-reserved memory as encrypted for SEV

Some drivers require memory that is marked as EFI boot services
data. In order for this memory to not be re-used by the kernel
after ExitBootServices(), efi_mem_reserve() is used to preserve it
by inserting a new EFI memory descriptor and marking it with the
EFI_MEMORY_RUNTIME attribute.

Under SEV, memory marked with the EFI_MEMORY_RUNTIME attribute needs to
be mapped encrypted by Linux, otherwise the kernel might crash at boot
like below:

  EFI Variables Facility v0.08 2004-May-17
  general protection fault, probably for non-canonical address 0x3597688770a868b2: 0000 [#1] SMP NOPTI
  CPU: 13 PID: 1 Comm: swapper/0 Not tainted 5.12.4-2-default #1 openSUSE Tumbleweed
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
  RIP: 0010:efi_mokvar_entry_next
  [...]
  Call Trace:
   efi_mokvar_sysfs_init
   ? efi_mokvar_table_init
   do_one_initcall
   ? __kmalloc
   kernel_init_freeable
   ? rest_init
   kernel_init
   ret_from_fork

Expand the __ioremap_check_other() function to additionally check for
this other type of boot data reserved at runtime and indicate that it
should be mapped encrypted for an SEV guest.

 [ bp: Massage commit message. ]

The Linux kernel CVE team has assigned CVE-2021-47228 to this issue.

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

	Issue introduced in 5.10 with commit 58c909022a5a and fixed in 5.10.46 with commit 208bb686e7fa
	Issue introduced in 5.10 with commit 58c909022a5a and fixed in 5.12.13 with commit b7a05aba39f7
	Issue introduced in 5.10 with commit 58c909022a5a and fixed in 5.13 with commit 8d651ee9c71b

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-2021-47228
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:
	arch/x86/mm/ioremap.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/208bb686e7fa7fff16e8fa78ff0db34aa9acdbd7
	https://git.kernel.org/stable/c/b7a05aba39f733ec337c5b952e112dd2dc4fc404
	https://git.kernel.org/stable/c/8d651ee9c71bb12fc0c8eb2786b66cbe5aa3e43b