[PATCH AUTOSEL 5.10 29/38] riscv: mm: Take memory hotplug read-lock during kernel page table dump

Sasha Levin
2024-08-01T00:38:33Z

From: Björn Töpel <bjorn@rivosinc.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@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20240605114100.315918-8-bjorn@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.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 ace74dec7492c..b5a8c7c20d120 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>

@@ -324,7 +325,9 @@ 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