From: Ard Biesheuvel ardb@kernel.org
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.
Cc: stable@vger.kernel.org # v6.1+ Cc: "H. Peter Anvin" hpa@zytor.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Ulrich Gemkow ulrich.gemkow@ikr.uni-stuttgart.de Closes: https://lore.kernel.org/all/202503041549.35913.ulrich.gemkow@ikr.uni-stuttga... Signed-off-by: Ard Biesheuvel ardb@kernel.org --- arch/x86/boot/compressed/pgtable_64.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index c882e1f67af0..d8c5de40669d 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -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;
/*
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 ardb@kernel.org AuthorDate: Thu, 06 Mar 2025 16:59:16 +01:00 Committer: Ingo Molnar mingo@kernel.org 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.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Cc: "H. Peter Anvin" hpa@zytor.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: stable@vger.kernel.org # v6.1+ Link: https://lore.kernel.org/r/20250306155915.342465-2-ardb+git@google.com Closes: https://lore.kernel.org/all/202503041549.35913.ulrich.gemkow@ikr.uni-stuttga... --- arch/x86/boot/compressed/pgtable_64.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index c882e1f..d8c5de4 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -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;
/*
On Thu, Mar 06, 2025 at 04:59:16PM +0100, Ard Biesheuvel wrote:
From: Ard Biesheuvel ardb@kernel.org
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.
Cc: stable@vger.kernel.org # v6.1+ Cc: "H. Peter Anvin" hpa@zytor.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Ulrich Gemkow ulrich.gemkow@ikr.uni-stuttgart.de Closes: https://lore.kernel.org/all/202503041549.35913.ulrich.gemkow@ikr.uni-stuttga... Signed-off-by: Ard Biesheuvel ardb@kernel.org
Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com
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