37 lines
1.2 KiB
Diff
37 lines
1.2 KiB
Diff
From: Matthew Garrett <matthewgarrett@google.com>
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Date: Wed, 31 Jul 2019 15:16:16 -0700
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Subject: efi: Restrict efivar_ssdt_load when the kernel is locked down
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Origin: https://patchwork.kernel.org/patch/11069659/
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efivar_ssdt_load allows the kernel to import arbitrary ACPI code from an
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EFI variable, which gives arbitrary code execution in ring 0. Prevent
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that when the kernel is locked down.
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Signed-off-by: Matthew Garrett <mjg59@google.com>
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Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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Reviewed-by: Kees Cook <keescook@chromium.org>
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Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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Cc: linux-efi@vger.kernel.org
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[bwh: Convert back to the non-LSM lockdown API]
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---
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--- a/drivers/firmware/efi/efi.c
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+++ b/drivers/firmware/efi/efi.c
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@@ -30,6 +30,7 @@
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#include <linux/acpi.h>
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#include <linux/ucs2_string.h>
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#include <linux/memblock.h>
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+#include <linux/security.h>
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#include <asm/early_ioremap.h>
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@@ -241,6 +242,9 @@ static void generic_ops_unregister(void)
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static char efivar_ssdt[EFIVAR_SSDT_NAME_MAX] __initdata;
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static int __init efivar_ssdt_setup(char *str)
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{
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+ if (kernel_is_locked_down("ACPI tables"))
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+ return -EPERM;
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+
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if (strlen(str) < sizeof(efivar_ssdt))
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memcpy(efivar_ssdt, str, strlen(str));
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else
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