linux-kernel - [PATCH] efi/x86: fix boot regression on systems with invalid memmap entries

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Message-Id: <20200201233304.18322-1-ardb@kernel.org>
Date:   Sun,  2 Feb 2020 00:33:04 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-efi@...r.kernel.org
Cc:     x86@...nel.org, dan.j.williams@...el.com, jrg.otte@...il.com,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        mingo@...nel.org, Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH] efi/x86: fix boot regression on systems with invalid memmap entries

In efi_clean_memmap(), we do a pass over the EFI memory map to remove
bogus entries that may be returned on certain systems.

Commit 1db91035d01aa8bf ("efi: Add tracking for dynamically allocated
memmaps") refactored this code to pass the input to efi_memmap_install()
via a temporary struct on the stack, which is populated using an
initializer which inadvertently defines the value of its size field
in terms of its desc_size field, which value cannot be relied upon yet
in the initializer itself.

Fix this by using efi.memmap.desc_size instead, which is where we get
the value for desc_size from in the first place.

Tested-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/platform/efi/efi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 59f7f6d60cf6..ae923ee8e2b4 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -308,7 +308,7 @@ static void __init efi_clean_memmap(void)
 			.phys_map = efi.memmap.phys_map,
 			.desc_version = efi.memmap.desc_version,
 			.desc_size = efi.memmap.desc_size,
-			.size = data.desc_size * (efi.memmap.nr_map - n_removal),
+			.size = efi.memmap.desc_size * (efi.memmap.nr_map - n_removal),
 			.flags = 0,
 		};

-- 
2.17.1