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From: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn@kernel.org>
To: Alexandre Ghiti <alexghiti@rivosinc.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	David Hildenbrand <david@redhat.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org,
	Oscar Salvador <osalvador@suse.de>
Cc: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn@rivosinc.com>,
	Andrew Bresticker <abrestic@rivosinc.com>,
	Chethan Seshadri <Chethan.Seshadri@catalinasystems.io>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Santosh Mamila <santosh.mamila@catalinasystems.io>,
	Sivakumar Munnangi <siva.munnangi@catalinasystems.io>,
	Sunil V L <sunilvl@ventanamicro.com>,
	linux-kernel@vger.kernel.org,
	linux-mm@kvack.org,
	virtualization@lists.linux-foundation.org
Subject: [PATCH v3 6/9] riscv: mm: Take memory hotplug read-lock during kernel page table dump
Date: Tue, 21 May 2024 13:48:27 +0200
Message-Id: <20240521114830.841660-7-bjorn@kernel.org>
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From: Björn Töpel <bjorn@rivosinc.com>

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@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
---
 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 1289cc6d3700..9d5f657a251b 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>
 
@@ -370,7 +371,9 @@ bool 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;
 }
-- 
2.40.1