From: Anshuman Khandual anshuman.khandual@arm.com
[ Upstream commit bf2b59f60ee1fefa768d62ec6e8f4b4d9e04c691 ]
The arm64 page table dump code can race with concurrent modification of the kernel page tables. When a leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful.
When intermediate levels of table are freed, the dump code will continue to use memory which has been freed and potentially reallocated for another purpose. In such cases, the dump code may dereference bogus addresses, leading to a number of potential problems.
Intermediate levels of table may by freed during memory hot-remove, which will be enabled by a subsequent patch. To avoid racing with this, take the memory hotplug lock when walking the kernel page table.
Acked-by: David Hildenbrand david@redhat.com Acked-by: Mark Rutland mark.rutland@arm.com Acked-by: Catalin Marinas catalin.marinas@arm.com Reviewed-by: Steven Price steven.price@arm.com Signed-off-by: Anshuman Khandual anshuman.khandual@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/mm/ptdump_debugfs.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c index 1f2eae3e988b6..d29d722ec3ec6 100644 --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/debugfs.h> +#include <linux/memory_hotplug.h> #include <linux/seq_file.h>
#include <asm/ptdump.h> @@ -7,7 +8,10 @@ static int ptdump_show(struct seq_file *m, void *v) { struct ptdump_info *info = m->private; + + get_online_mems(); ptdump_walk(m, info); + put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump);