linux-kernel - [PATCH AUTOSEL 5.15 36/47] riscv: mm: Take memory hotplug read-lock during kernel page table dump

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Message-ID: <20240801003256.3937416-36-sashal@kernel.org>
Date: Wed, 31 Jul 2024 20:31:26 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Björn Töpel <bjorn@...osinc.com>,
	David Hildenbrand <david@...hat.com>,
	Oscar Salvador <osalvador@...e.de>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Sasha Levin <sashal@...nel.org>,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alexghiti@...osinc.com,
	peterlin@...estech.com,
	akpm@...ux-foundation.org,
	christophe.leroy@...roup.eu,
	suagrfillet@...il.com,
	linux-riscv@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.15 36/47] riscv: mm: Take memory hotplug read-lock during kernel page table dump

From: Björn Töpel <bjorn@...osinc.com>

[ Upstream commit 37992b7f1097ba79ca75ba5a26ddcf0f54f91a08 ]

During memory hot remove, the ptdump functionality can end up touching
stale data. Avoid any potential crashes (or worse), by holding the
memory hotplug read-lock while traversing the page table.

This change is analogous to arm64's commit bf2b59f60ee1 ("arm64/mm:
Hold memory hotplug lock while walking for kernel page table dump").

Reviewed-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
Signed-off-by: Björn Töpel <bjorn@...osinc.com>
Link: https://lore.kernel.org/r/20240605114100.315918-8-bjorn@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/riscv/mm/ptdump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
index 830e7de65e3a3..154cc427f4957 100644
--- a/arch/riscv/mm/ptdump.c
+++ b/arch/riscv/mm/ptdump.c
@@ -6,6 +6,7 @@
 #include <linux/efi.h>
 #include <linux/init.h>
 #include <linux/debugfs.h>
+#include <linux/memory_hotplug.h>
 #include <linux/seq_file.h>
 #include <linux/ptdump.h>
 
@@ -351,7 +352,9 @@ void ptdump_check_wx(void)
 
 static int ptdump_show(struct seq_file *m, void *v)
 {
+	get_online_mems();
 	ptdump_walk(m, m->private);
+	put_online_mems();
 
 	return 0;
 }
-- 
2.43.0