FAILED: patch "[PATCH] x86/boot: Sanitize boot params before parsing command line" failed to apply to 6.6-stable tree

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 <[email protected]>.

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 '<[email protected]>' --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 <[email protected]>
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.

index c882e1f67af0..d8c5de40669d 100644
@@ -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;
 
 	/*