linux-kernel - [tip:efi/urgent] x86/efi: Disable runtime services on kexec kernel if booted with efi=old

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Message-ID: <tip-4e52797d2efefac3271abdc54439a3435abd77b9@git.kernel.org>
Date:   Sun, 28 May 2017 02:45:26 -0700
From:   tip-bot for Sai Praneeth <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     bp@...en8.de, jlee@...e.com, hpa@...or.com, tglx@...utronix.de,
        matt@...eblueprint.co.uk, peterz@...radead.org, mingo@...nel.org,
        dyoung@...hat.com, ricardo.neri@...el.com,
        ravi.v.shankar@...el.com, torvalds@...ux-foundation.org,
        sai.praneeth.prakhya@...el.com, linux-kernel@...r.kernel.org,
        ard.biesheuvel@...aro.org
Subject: [tip:efi/urgent] x86/efi: Disable runtime services on kexec kernel
 if booted with efi=old_map

Commit-ID:  4e52797d2efefac3271abdc54439a3435abd77b9
Gitweb:     http://git.kernel.org/tip/4e52797d2efefac3271abdc54439a3435abd77b9
Author:     Sai Praneeth <sai.praneeth.prakhya@...el.com>
AuthorDate: Fri, 26 May 2017 12:36:49 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 28 May 2017 11:06:16 +0200

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

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@...e.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Acked-by: Dave Young <dyoung@...hat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>
Cc: Ricardo Neri <ricardo.neri@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Link: http://lkml.kernel.org/r/20170526113652.21339-4-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/platform/efi/efi.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 7e76a4d..43b96f5 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -828,9 +828,11 @@ static void __init kexec_enter_virtual_mode(void)
 
 	/*
 	 * 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;