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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Miaohe Lin <linmiaohe@huawei.com>,
        David Hildenbrand <david@redhat.com>,
        Alistair Popple <apopple@nvidia.com>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Howells <dhowells@redhat.com>,
        Huang Ying <ying.huang@intel.com>,
        kernel test robot <lkp@intel.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Oscar Salvador <osalvador@suse.de>,
        Peter Xu <peterx@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.18 0717/1095] mm/migration: fix potential pte_unmap on an not mapped pte
Date:   Mon, 15 Aug 2022 20:01:56 +0200
Message-Id: <20220815180459.050073088@linuxfoundation.org>
In-Reply-To: <20220815180429.240518113@linuxfoundation.org>
References: <20220815180429.240518113@linuxfoundation.org>
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From: Miaohe Lin <linmiaohe@huawei.com>

[ Upstream commit ad1ac596e8a8c4b06715dfbd89853eb73c9886b2 ]

__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/20220530113016.16663-5-linmiaohe@huawei.com
Fixes: 30dad30922cc ("mm: migration: add migrate_entry_wait_huge()")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/swapops.h | 12 ++++++++----
 mm/hugetlb.c            |  4 ++--
 mm/migrate.c            | 23 +++++++++++++++++++----
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index d356ab4047f7..f99f0bd85724 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -216,8 +216,10 @@ 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)
 {
@@ -238,8 +240,10 @@ 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
index 0090d7f98dee..19063dbed332 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5602,7 +5602,7 @@ 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 |
@@ -6725,7 +6725,7 @@ 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
index 796502d0eeb9..5aba3fb612d4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -309,13 +309,28 @@ 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)
 {
-- 
2.35.1