+ kho-fix-boot-failure-due-to-kmemleak-access-to-non-present-pages.patch added to mm-nonmm-unstable branch

+ kho-fix-boot-failure-due-to-kmemleak-access-to-non-present-pages.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: KHO: fix boot failure due to kmemleak access to non-PRESENT pages
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kho-fix-boot-failure-due-to-kmemleak-access-to-non-present-pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kho-fix-boot-failure-due-to-kmemleak-access-to-non-present-pages.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Subject: KHO: fix boot failure due to kmemleak access to non-PRESENT pages
Date: Sat, 22 Nov 2025 18:29:29 +0000

When booting with debug_pagealloc=on while having:
CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y
CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=n
the system fails to boot due to page faults during kmemleak scanning.

This occurs because:
With debug_pagealloc is enabled, __free_pages() invokes
debug_pagealloc_unmap_pages(), clearing the _PAGE_PRESENT bit for
freed pages in the kernel page table.
Commit 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
triggers this when releases the KHO scratch region calling
init_cma_reserved_pageblock(). Subsequent kmemleak scanning accesses
these non-PRESENT pages, leading to fatal page faults.

Call kmemleak_ignore_phys() from kho_init() to exclude the reserved region
from kmemleak scanning before it is released to the buddy allocator to fix
this.

Link: https://lkml.kernel.org/r/20251122182929.92634-1-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Alexander Graf <graf@amazon.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/liveupdate/kexec_handover.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/kernel/liveupdate/kexec_handover.c~kho-fix-boot-failure-due-to-kmemleak-access-to-non-present-pages
+++ a/kernel/liveupdate/kexec_handover.c
@@ -11,6 +11,7 @@
 
 #include <linux/cleanup.h>
 #include <linux/cma.h>
+#include <linux/kmemleak.h>
 #include <linux/count_zeros.h>
 #include <linux/kexec.h>
 #include <linux/kexec_handover.h>
@@ -1369,6 +1370,7 @@ static __init int kho_init(void)
 		unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
 		unsigned long pfn;
 
+		kmemleak_ignore_phys(kho_scratch[i].addr);
 		for (pfn = base_pfn; pfn < base_pfn + count;
 		     pfn += pageblock_nr_pages)
 			init_cma_reserved_pageblock(pfn_to_page(pfn));
_

Patches currently in -mm which might be from ran.xiaokai@zte.com.cn are

kho-fix-boot-failure-due-to-kmemleak-access-to-non-present-pages.patch