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Subject[PATCH 4.11 049/150] efi/bgrt: Skip efi_bgrt_init() in case of non-EFI boot
Date
4.11-stable review patch.  If anyone has any objections, please let me know.

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

From: Dave Young <dyoung@redhat.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@queasysnail.net>
Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.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@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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));

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