arm64: Restrict pagetable teardown to avoid false warning

commit 650768c512faba8070bf4cfbb28c95eb5cd203f3 upstream.

Commit 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from
pXd_free_pYd_table()") removes the pxd_present() checks because the
caller checks pxd_present(). But, in case of vmap_try_huge_pud(), the
caller only checks pud_present(); pud_free_pmd_page() recurses on each
pmd through pmd_free_pte_page(), wherein the pmd may be none. Thus it is
possible to hit a warning in the latter, since pmd_none => !pmd_table().
Thus, add a pmd_present() check in pud_free_pmd_page().

This problem was found by code inspection.

Fixes: 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from pXd_free_pYd_table()")
Cc: stable@vger.kernel.org
Reported-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20250527082633.61073-1-dev.jain@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8e934bb44f12e76aca77b18c2847814975884a19..ef94bf75b433be3d8144c7db3f7c4cea0fc2f89e 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1041,7 +1041,8 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
        next = addr;
        end = addr + PUD_SIZE;
        do {
-               pmd_free_pte_page(pmdp, next);
+               if (pmd_present(READ_ONCE(*pmdp)))
+                       pmd_free_pte_page(pmdp, next);
        } while (pmdp++, next += PMD_SIZE, next != end);
 
        pud_clear(pudp);