[PATCH v3 6/9] riscv: mm: Take memory hotplug read-lock during kernel page table dump

[Björn Töpel <bjorn@xxxxxxxxxx>]

From: Björn Töpel <bjorn@xxxxxxxxxxxx>

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@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
---
 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