linux-kernel - [PATCH 2/2] liveupdate: Fix boot failure due to kmemleak access to unmapped pages

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Message-ID: <20251120144147.90508-3-ranxiaokai627@163.com>
Date: Thu, 20 Nov 2025 14:41:47 +0000
From: ranxiaokai627@....com
To: catalin.marinas@....com,
	akpm@...ux-foundation.org,
	graf@...zon.com,
	rppt@...nel.org,
	pasha.tatashin@...een.com,
	pratyush@...nel.org,
	changyuanl@...gle.com
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	kexec@...ts.infradead.org,
	ran.xiaokai@....com.cn,
	ranxiaokai627@....com
Subject: [PATCH 2/2] liveupdate: Fix boot failure due to kmemleak access to unmapped pages

From: Ran Xiaokai <ran.xiaokai@....com.cn>

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 enabled, __free_pages() invokes
debug_pagealloc_unmap_pages(), clearing the _PAGE_PRESENT bit for
freed pages in the direct mapping.
Commit 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
releases the KHO scratch region via init_cma_reserved_pageblock(),
unmapping its physical pages. Subsequent kmemleak scanning accesses
these unmapped pages, triggering fatal page faults.

Call kmemleak_no_scan_phys() from kho_reserve_scratch() to
exclude the reserved region from scanning before
it is released to the buddy allocator.

Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
---
 kernel/liveupdate/kexec_handover.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 224bdf5becb6..dd4942d1d76c 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/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>
@@ -654,6 +655,7 @@ static void __init kho_reserve_scratch(void)
 	if (!addr)
 		goto err_free_scratch_desc;
 
+	kmemleak_no_scan_phys(addr);
 	kho_scratch[i].addr = addr;
 	kho_scratch[i].size = size;
 	i++;
@@ -664,6 +666,7 @@ static void __init kho_reserve_scratch(void)
 	if (!addr)
 		goto err_free_scratch_areas;
 
+	kmemleak_no_scan_phys(addr);
 	kho_scratch[i].addr = addr;
 	kho_scratch[i].size = size;
 	i++;
@@ -676,6 +679,7 @@ static void __init kho_reserve_scratch(void)
 		if (!addr)
 			goto err_free_scratch_areas;
 
+		kmemleak_no_scan_phys(addr);
 		kho_scratch[i].addr = addr;
 		kho_scratch[i].size = size;
 		i++;
-- 
2.25.1