This is a note to let you know that I've just added the patch titled
efi: use 32-bit alignment for efi_guid_t literals
to the 5.10-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:
efi-use-32-bit-alignment-for-efi_guid_t-literals.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fb98cc0b3af2ba4d87301dff2b381b12eee35d7d Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@xxxxxxxxxx>
Date: Wed, 10 Mar 2021 08:33:19 +0100
Subject: efi: use 32-bit alignment for efi_guid_t literals
From: Ard Biesheuvel <ardb@xxxxxxxxxx>
commit fb98cc0b3af2ba4d87301dff2b381b12eee35d7d upstream.
Commit 494c704f9af0 ("efi: Use 32-bit alignment for efi_guid_t") updated
the type definition of efi_guid_t to ensure that it always appears
sufficiently aligned (the UEFI spec is ambiguous about this, but given
the fact that its EFI_GUID type is defined in terms of a struct carrying
a uint32_t, the natural alignment is definitely >= 32 bits).
However, we missed the EFI_GUID() macro which is used to instantiate
efi_guid_t literals: that macro is still based on the guid_t type,
which does not have a minimum alignment at all. This results in warnings
such as
In file included from drivers/firmware/efi/mokvar-table.c:35:
include/linux/efi.h:1093:34: warning: passing 1-byte aligned argument to
4-byte aligned parameter 2 of 'get_var' may result in an unaligned pointer
access [-Walign-mismatch]
status = get_var(L"SecureBoot", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size,
^
include/linux/efi.h:1101:24: warning: passing 1-byte aligned argument to
4-byte aligned parameter 2 of 'get_var' may result in an unaligned pointer
access [-Walign-mismatch]
get_var(L"SetupMode", &EFI_GLOBAL_VARIABLE_GUID, NULL, &size, &setupmode);
The distinction only matters on CPUs that do not support misaligned loads
fully, but 32-bit ARM's load-multiple instructions fall into that category,
and these are likely to be emitted by the compiler that built the firmware
for loading word-aligned 128-bit GUIDs from memory
So re-implement the initializer in terms of our own efi_guid_t type, so that
the alignment becomes a property of the literal's type.
Fixes: 494c704f9af0 ("efi: Use 32-bit alignment for efi_guid_t")
Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Link: https://github.com/ClangBuiltLinux/linux/issues/1327
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/efi.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -72,8 +72,10 @@ typedef void *efi_handle_t;
*/
typedef guid_t efi_guid_t __aligned(__alignof__(u32));
-#define EFI_GUID(a,b,c,d0,d1,d2,d3,d4,d5,d6,d7) \
- GUID_INIT(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)
+#define EFI_GUID(a, b, c, d...) (efi_guid_t){ { \
+ (a) & 0xff, ((a) >> 8) & 0xff, ((a) >> 16) & 0xff, ((a) >> 24) & 0xff, \
+ (b) & 0xff, ((b) >> 8) & 0xff, \
+ (c) & 0xff, ((c) >> 8) & 0xff, d } }
/*
* Generic EFI table header
Patches currently in stable-queue which might be from ardb@xxxxxxxxxx are
queue-5.10/efi-use-32-bit-alignment-for-efi_guid_t-literals.patch
queue-5.10/efivars-respect-efi_unsupported-return-from-firmware.patch
queue-5.10/firmware-efi-fix-a-use-after-bug-in-efi_mem_reserve_persistent.patch
