Subject: [PATCH V3 4/6] arch/powerpc/mm/hash: validate the pte entries before handling the hash fault

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Thu, 20 Sep 2018 23:39:45 +0530

Make sure we are operating on THP and hugetlb entries in the respective hash
fault handling routines.

No functional change in this patch. If we walked the table wrongly before, we
will retry the access.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/powerpc/mm/hugepage-hash64.c    | 6 ++++++
 arch/powerpc/mm/hugetlbpage-hash64.c | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/arch/powerpc/mm/hugepage-hash64.c b/arch/powerpc/mm/hugepage-hash64.c
index 01f213d2bcb9..dfbc3b32f09b 100644
--- a/arch/powerpc/mm/hugepage-hash64.c
+++ b/arch/powerpc/mm/hugepage-hash64.c
@@ -51,6 +51,12 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
 			new_pmd |= _PAGE_DIRTY;
 	} while (!pmd_xchg(pmdp, __pmd(old_pmd), __pmd(new_pmd)));
 
+	/*
+	 * Make sure this is thp or devmap entry
+	 */
+	if (!(old_pmd & (H_PAGE_THP_HUGE | _PAGE_DEVMAP)))
+		return 0;
+
 	rflags = htab_convert_pte_flags(new_pmd);
 
 #if 0
diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
index b320f5097a06..2e6a8f9345d3 100644
--- a/arch/powerpc/mm/hugetlbpage-hash64.c
+++ b/arch/powerpc/mm/hugetlbpage-hash64.c
@@ -62,6 +62,10 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
 			new_pte |= _PAGE_DIRTY;
 	} while(!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
 
+	/* Make sure this is a hugetlb entry */
+	if (old_pte & (H_PAGE_THP_HUGE | _PAGE_DEVMAP))
+		return 0;
+
 	rflags = htab_convert_pte_flags(new_pte);
 	if (unlikely(mmu_psize == MMU_PAGE_16G))
 		offset = PTRS_PER_PUD;
-- 
2.17.1