The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x c00b413a96261faef4ce22329153c6abd4acef25 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025030905-smooth-making-7a63@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c00b413a96261faef4ce22329153c6abd4acef25 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel ardb@kernel.org Date: Thu, 6 Mar 2025 16:59:16 +0100 Subject: [PATCH] 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...

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;

/*