x86/boot: Sanitize boot params before parsing command line
Subsystems (2)
PATCH 1/1 x86/boot: Sanitize boot params before parsing command line
From: Ard Biesheuvel <[email protected]>
The 5-level paging code parses the command line to look for the 'no5lvl' string, and does so very early, before sanitize_boot_params() has been called and has been given the opportunity to wipe bogus data from the fields in boot_params that are not covered by struct setup_header, and are therefore supposed to be initialized to zero by the bootloader.
This triggers an early boot crash when using syslinux-efi to boot a recent kernel built with CONFIG_X86_5LEVEL=y and CONFIG_EFI_STUB=n, as the 0xff padding that now fills the unused PE/COFF header is copied into boot_params by the bootloader, and interpreted as the top half of the command line pointer.
Fix this by sanitizing the boot_params before use. Note that there is no harm in calling this more than once; subsequent invocations are able to spot that the boot_params have already been cleaned up.
--- arch/x86/boot/compressed/pgtable_64.c | 2 ++ 1 file changed, 2 insertions(+)
arch/x86/boot/compressed/pgtable_64.c +2 -0
@@ -1,6 +1,7 @@// SPDX-License-Identifier: GPL-2.0 #include "misc.h" #include <asm/bootparam.h> +#include <asm/bootparam_utils.h> #include <asm/e820/types.h> #include <asm/processor.h> #include "pgtable.h"
@@ -107,6 +108,7 @@ asmlinkage void configure_5level_paging(struct boot_params *bp, void *pgtable)bool l5_required = false;/* Initialize boot_params. Required for cmdline_find_option_bool(). */ +sanitize_boot_params (bp); boot_params_ptr = bp;/*
Signature · 1 line
2.48.1.711.g2feabab25a-goog
The following commit has been merged into the x86/urgent branch of tip:
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: c00b413a96261faef4ce22329153c6abd4acef25 Gitweb: https://git.kernel.org/tip/c00b413a96261faef4ce22329153c6abd4acef25 Author: Ard Biesheuvel <[email protected]> AuthorDate: Thu, 06 Mar 2025 16:59:16 +01:00 Committer: Ingo Molnar <[email protected]> CommitterDate: Thu, 06 Mar 2025 22:02:39 +01:00
x86/boot: Sanitize boot params before parsing command line
The 5-level paging code parses the command line to look for the 'no5lvl' string, and does so very early, before sanitize_boot_params() has been called and has been given the opportunity to wipe bogus data from the fields in boot_params that are not covered by struct setup_header, and are therefore supposed to be initialized to zero by the bootloader.
This triggers an early boot crash when using syslinux-efi to boot a recent kernel built with CONFIG_X86_5LEVEL=y and CONFIG_EFI_STUB=n, as the 0xff padding that now fills the unused PE/COFF header is copied into boot_params by the bootloader, and interpreted as the top half of the command line pointer.
Fix this by sanitizing the boot_params before use. Note that there is no harm in calling this more than once; subsequent invocations are able to spot that the boot_params have already been cleaned up.
--- arch/x86/boot/compressed/pgtable_64.c | 2 ++ 1 file changed, 2 insertions(+)
arch/x86/boot/compressed/pgtable_64.c +2 -0
@@ -1,6 +1,7 @@// SPDX-License-Identifier: GPL-2.0 #include "misc.h" #include <asm/bootparam.h> +#include <asm/bootparam_utils.h> #include <asm/e820/types.h> #include <asm/processor.h> #include "pgtable.h"
@@ -107,6 +108,7 @@ asmlinkage void configure_5level_paging(struct boot_params *bp, void *pgtable)bool l5_required = false;/* Initialize boot_params. Required for cmdline_find_option_bool(). */ +sanitize_boot_params (bp); boot_params_ptr = bp;/*
Quoted 18 lines · Ard Biesheuvel
From: Ard Biesheuvel <[email protected]>
The 5-level paging code parses the command line to look for the 'no5lvl' string, and does so very early, before
sanitize_boot_params()has been called and has been given the opportunity to wipe bogus data from the fields inboot_paramsthat are not covered by structsetup_header, and are therefore supposed to be initialized to zero by the bootloader.This triggers an early boot crash when using syslinux-efi to boot a recent kernel built with
CONFIG_X86_5LEVEL=yandCONFIG_EFI_STUB=n, as the0xffpadding that now fills the unused PE/COFF header is copied intoboot_paramsby the bootloader, and interpreted as the top half of the command line pointer.Fix this by sanitizing the
boot_paramsbefore use. Note that there is no harm in calling this more than once; subsequent invocations are able to spot that theboot_paramshave already been cleaned up.
Quoted 6 lines
Cc <[email protected]> # v6.1+Cc "H. Peter Anvin" <[email protected]>Cc "Kirill A. Shutemov" <[email protected]>Cc Ulrich Gemkow <[email protected]>Signed-off-by Ard Biesheuvel <[email protected]>
Signature · 1 line
Kiryl Shutsemau / Kirill A. Shutemov