Patch "x86/efi: Disable runtime services on kexec kernel if booted with efi=old_map" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    x86/efi: Disable runtime services on kexec kernel if booted with efi=old_map

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-efi-disable-runtime-services-on-kexec-kernel-if-booted-with-efi-old_map.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Apr  9 17:09:24 CEST 2018
From: Sai Praneeth <sai.praneeth.prakhya@intel.com>
Date: Fri, 26 May 2017 12:36:49 +0100
Subject: x86/efi: Disable runtime services on kexec kernel if booted with efi=old_map

From: Sai Praneeth <sai.praneeth.prakhya@intel.com>


[ Upstream commit 4e52797d2efefac3271abdc54439a3435abd77b9 ]

Booting kexec kernel with "efi=old_map" in kernel command line hits
kernel panic as shown below.

 BUG: unable to handle kernel paging request at ffff88007fe78070
 IP: virt_efi_set_variable.part.7+0x63/0x1b0
 PGD 7ea28067
 PUD 7ea2b067
 PMD 7ea2d067
 PTE 0
 [...]
 Call Trace:
  virt_efi_set_variable()
  efi_delete_dummy_variable()
  efi_enter_virtual_mode()
  start_kernel()
  x86_64_start_reservations()
  x86_64_start_kernel()
  start_cpu()

[ efi=old_map was never intended to work with kexec. The problem with
  using efi=old_map is that the virtual addresses are assigned from the
  memory region used by other kernel mappings; vmalloc() space.
  Potentially there could be collisions when booting kexec if something
  else is mapped at the virtual address we allocated for runtime service
  regions in the initial boot - Matt Fleming ]

Since kexec was never intended to work with efi=old_map, disable
runtime services in kexec if booted with efi=old_map, so that we don't
panic.

Tested-by: Lee Chun-Yi <jlee@suse.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170526113652.21339-4-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/platform/efi/efi.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -832,9 +832,11 @@ static void __init kexec_enter_virtual_m
 
 	/*
 	 * We don't do virtual mode, since we don't do runtime services, on
-	 * non-native EFI
+	 * non-native EFI. With efi=old_map, we don't do runtime services in
+	 * kexec kernel because in the initial boot something else might
+	 * have been mapped at these virtual addresses.
 	 */
-	if (!efi_is_native()) {
+	if (!efi_is_native() || efi_enabled(EFI_OLD_MEMMAP)) {
 		efi_memmap_unmap();
 		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
 		return;


Patches currently in stable-queue which might be from sai.praneeth.prakhya@intel.com are

queue-4.9/x86-efi-disable-runtime-services-on-kexec-kernel-if-booted-with-efi-old_map.patch