mm/migration: fix potential pte_unmap on an not mapped pte

__migration_entry_wait and migration_entry_wait_on_locked assume pte is always mapped from caller. But this is not the case when it's called from migration_entry_wait_huge and follow_huge_pmd. Add a hugetlbfs variant that calls hugetlb_migration_entry_wait(ptep == NULL) to fix this issue. Link: https://lkml.kernel.org/r/[email protected] Fixes: 30dad30 ("mm: migration: add migrate_entry_wait_huge()") Signed-off-by: Miaohe Lin <[email protected]> Suggested-by: David Hildenbrand <[email protected]> Reviewed-by: David Hildenbrand <[email protected]> Cc: Alistair Popple <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: David Howells <[email protected]> Cc: Huang Ying <[email protected]> Cc: kernel test robot <[email protected]> Cc: Mike Kravetz <[email protected]> Cc: Muchun Song <[email protected]> Cc: Oscar Salvador <[email protected]> Cc: Peter Xu <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
ambv · Jul 4, 2022 · ad1ac59 · ad1ac59
1 parent 7ce82f4
commit ad1ac59
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Showing 3 changed files with 29 additions and 10 deletions.
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
@@ -244,8 +244,10 @@ extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
 					spinlock_t *ptl);
 extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 					unsigned long address);
-extern void migration_entry_wait_huge(struct vm_area_struct *vma,
-		struct mm_struct *mm, pte_t *pte);
+#ifdef CONFIG_HUGETLB_PAGE
+extern void __migration_entry_wait_huge(pte_t *ptep, spinlock_t *ptl);
+extern void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte);
+#endif
 #else
 static inline swp_entry_t make_readable_migration_entry(pgoff_t offset)
 {
@@ -271,8 +273,10 @@ static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
 					spinlock_t *ptl) { }
 static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 					 unsigned long address) { }
-static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
-		struct mm_struct *mm, pte_t *pte) { }
+#ifdef CONFIG_HUGETLB_PAGE
+static inline void __migration_entry_wait_huge(pte_t *ptep, spinlock_t *ptl) { }
+static inline void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte) { }
+#endif
 static inline int is_writable_migration_entry(swp_entry_t entry)
 {
 	return 0;

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
@@ -5702,7 +5702,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		 */
 		entry = huge_ptep_get(ptep);
 		if (unlikely(is_hugetlb_entry_migration(entry))) {
-			migration_entry_wait_huge(vma, mm, ptep);
+			migration_entry_wait_huge(vma, ptep);
 			return 0;
 		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
 			return VM_FAULT_HWPOISON_LARGE |
@@ -6927,7 +6927,7 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 	} else {
 		if (is_hugetlb_entry_migration(pte)) {
 			spin_unlock(ptl);
-			__migration_entry_wait(mm, (pte_t *)pmd, ptl);
+			__migration_entry_wait_huge((pte_t *)pmd, ptl);
 			goto retry;
 		}
 		/*

diff --git a/mm/migrate.c b/mm/migrate.c
@@ -315,13 +315,28 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 	__migration_entry_wait(mm, ptep, ptl);
 }
 
-void migration_entry_wait_huge(struct vm_area_struct *vma,
-		struct mm_struct *mm, pte_t *pte)
+#ifdef CONFIG_HUGETLB_PAGE
+void __migration_entry_wait_huge(pte_t *ptep, spinlock_t *ptl)
 {
-	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
-	__migration_entry_wait(mm, pte, ptl);
+	pte_t pte;
+
+	spin_lock(ptl);
+	pte = huge_ptep_get(ptep);
+
+	if (unlikely(!is_hugetlb_entry_migration(pte)))
+		spin_unlock(ptl);
+	else
+		migration_entry_wait_on_locked(pte_to_swp_entry(pte), NULL, ptl);
 }
 
+void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte)
+{
+	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, pte);
+
+	__migration_entry_wait_huge(pte, ptl);
+}
+#endif
+
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 {