Debian: CVE-2021-47228: linux -- security update

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. ]