Re: [PATCH v3] arm64: Restrict pagetable teardown to avoid false warning
From: Anshuman Khandual <hidden>
Date: 2025-05-29 09:02:38
Also in:
lkml, stable
On 5/27/25 13:56, Dev Jain wrote:
quoted hunk ↗ jump to hunk
Commit 9c006972c3fe 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: <redacted> Reported-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: David Hildenbrand <redacted> Signed-off-by: Dev Jain <dev.jain@arm.com> --- This patch is based on 6.15-rc6. v2->v3: - Use pmdp_get() v1->v2: - Enforce check in caller arch/arm64/mm/mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index ea6695d53fb9..5a9bf291c649 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c@@ -1286,7 +1286,8 @@ 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(pmdp_get(pmdp)))
This code path is only called for the kernel mapping. Hence should pmd_valid() be used instead of pmd_present() which also checks for present invalid scenarios as well ?
+ pmd_free_pte_page(pmdp, next); } while (pmdp++, next += PMD_SIZE, next != end); pud_clear(pudp);