On Mon, Jun 09, 2025 at 05:12:14AM +0100, Anshuman Khandual wrote:

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.

This problem was fixed for ptdump_show() earlier via commit 'bf2b59f60ee1
("arm64/mm: Hold memory hotplug lock while walking for kernel page table
dump")' but a same was missed for ptdump_check_wx() which faced the race
condition as well. Let's just take the memory hotplug lock while executing
ptdump_check_wx().

Cc: stable@vger.kernel.org
Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove")
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reported-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Anshuman Khandual <redacted>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>