linux-kernel - [PATCH 4.11 049/150] efi/bgrt: Skip efi_bgrt

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Date:   Mon, 12 Jun 2017 17:24:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sabrina Dubroca <sd@...asysnail.net>,
        Dave Young <dyoung@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.11 049/150] efi/bgrt: Skip efi_bgrt_init() in case of non-EFI boot

4.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Young <dyoung@...hat.com>

commit 7425826f4f7ac60f2538b06a7f0a5d1006405159 upstream.

Sabrina Dubroca reported an early panic:

  BUG: unable to handle kernel paging request at ffffffffff240001
  IP: efi_bgrt_init+0xdc/0x134

  [...]

  ---[ end Kernel panic - not syncing: Attempted to kill the idle task!

... which was introduced by:

  7b0a911478c7 ("efi/x86: Move the EFI BGRT init code to early init code")

The cause is that on this machine the firmware provides the EFI ACPI BGRT
table even on legacy non-EFI bootups - which table should be EFI only.

The garbage BGRT data causes the efi_bgrt_init() panic.

Add a check to skip efi_bgrt_init() in case non-EFI bootup to work around
this firmware bug.

Tested-by: Sabrina Dubroca <sd@...asysnail.net>
Signed-off-by: Dave Young <dyoung@...hat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Fixes: 7b0a911478c7 ("efi/x86: Move the EFI BGRT init code to early init code")
Link: http://lkml.kernel.org/r/20170526113652.21339-6-matt@codeblueprint.co.uk
[ Rewrote the changelog to be more readable. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/platform/efi/efi-bgrt.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/x86/platform/efi/efi-bgrt.c
+++ b/arch/x86/platform/efi/efi-bgrt.c
@@ -36,6 +36,9 @@ void __init efi_bgrt_init(struct acpi_ta
 	if (acpi_disabled)
 		return;

+	if (!efi_enabled(EFI_BOOT))
+		return;
+
 	if (table->length < sizeof(bgrt_tab)) {
 		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
 		       table->length, sizeof(bgrt_tab));