--- /dev/null
+From fac35ba763ed07ba93154c95ffc0c4a55023707f Mon Sep 17 00:00:00 2001
+From: Baolin Wang <baolin.wang@linux.alibaba.com>
+Date: Thu, 1 Sep 2022 18:41:31 +0800
+Subject: mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page
+
+From: Baolin Wang <baolin.wang@linux.alibaba.com>
+
+commit fac35ba763ed07ba93154c95ffc0c4a55023707f upstream.
+
+On some architectures (like ARM64), it can support CONT-PTE/PMD size
+hugetlb, which means it can support not only PMD/PUD size hugetlb (2M and
+1G), but also CONT-PTE/PMD size(64K and 32M) if a 4K page size specified.
+
+So when looking up a CONT-PTE size hugetlb page by follow_page(), it will
+use pte_offset_map_lock() to get the pte entry lock for the CONT-PTE size
+hugetlb in follow_page_pte(). However this pte entry lock is incorrect
+for the CONT-PTE size hugetlb, since we should use huge_pte_lock() to get
+the correct lock, which is mm->page_table_lock.
+
+That means the pte entry of the CONT-PTE size hugetlb under current pte
+lock is unstable in follow_page_pte(), we can continue to migrate or
+poison the pte entry of the CONT-PTE size hugetlb, which can cause some
+potential race issues, even though they are under the 'pte lock'.
+
+For example, suppose thread A is trying to look up a CONT-PTE size hugetlb
+page by move_pages() syscall under the lock, however antoher thread B can
+migrate the CONT-PTE hugetlb page at the same time, which will cause
+thread A to get an incorrect page, if thread A also wants to do page
+migration, then data inconsistency error occurs.
+
+Moreover we have the same issue for CONT-PMD size hugetlb in
+follow_huge_pmd().
+
+To fix above issues, rename the follow_huge_pmd() as follow_huge_pmd_pte()
+to handle PMD and PTE level size hugetlb, which uses huge_pte_lock() to
+get the correct pte entry lock to make the pte entry stable.
+
+Mike said:
+
+Support for CONT_PMD/_PTE was added with bb9dd3df8ee9 ("arm64: hugetlb:
+refactor find_num_contig()"). Patch series "Support for contiguous pte
+hugepages", v4. However, I do not believe these code paths were
+executed until migration support was added with 5480280d3f2d ("arm64/mm:
+enable HugeTLB migration for contiguous bit HugeTLB pages") I would go
+with 5480280d3f2d for the Fixes: targe.
+
+Link: https://lkml.kernel.org/r/635f43bdd85ac2615a58405da82b4d33c6e5eb05.1662017562.git.baolin.wang@linux.alibaba.com
+Fixes: 5480280d3f2d ("arm64/mm: enable HugeTLB migration for contiguous bit HugeTLB pages")
+Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
+Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
+Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
+Cc: David Hildenbrand <david@redhat.com>
+Cc: Muchun Song <songmuchun@bytedance.com>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+[5.4: Fixup contextual diffs before pin_user_pages()]
+Signed-off-by: Samuel Mendoza-Jonas <samjonas@amazon.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ include/linux/hugetlb.h | 6 +++---
+ mm/gup.c | 13 ++++++++++++-
+ mm/hugetlb.c | 30 +++++++++++++++---------------
+ 3 files changed, 30 insertions(+), 19 deletions(-)
+
+--- a/include/linux/hugetlb.h
++++ b/include/linux/hugetlb.h
+@@ -127,8 +127,8 @@ struct page *follow_huge_addr(struct mm_
+ struct page *follow_huge_pd(struct vm_area_struct *vma,
+ unsigned long address, hugepd_t hpd,
+ int flags, int pdshift);
+-struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
+- pmd_t *pmd, int flags);
++struct page *follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address,
++ int flags);
+ struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
+ pud_t *pud, int flags);
+ struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
+@@ -175,7 +175,7 @@ static inline void hugetlb_show_meminfo(
+ {
+ }
+ #define follow_huge_pd(vma, addr, hpd, flags, pdshift) NULL
+-#define follow_huge_pmd(mm, addr, pmd, flags) NULL
++#define follow_huge_pmd_pte(vma, addr, flags) NULL
+ #define follow_huge_pud(mm, addr, pud, flags) NULL
+ #define follow_huge_pgd(mm, addr, pgd, flags) NULL
+ #define prepare_hugepage_range(file, addr, len) (-EINVAL)
+--- a/mm/gup.c
++++ b/mm/gup.c
+@@ -188,6 +188,17 @@ static struct page *follow_page_pte(stru
+ spinlock_t *ptl;
+ pte_t *ptep, pte;
+
++ /*
++ * Considering PTE level hugetlb, like continuous-PTE hugetlb on
++ * ARM64 architecture.
++ */
++ if (is_vm_hugetlb_page(vma)) {
++ page = follow_huge_pmd_pte(vma, address, flags);
++ if (page)
++ return page;
++ return no_page_table(vma, flags);
++ }
++
+ retry:
+ if (unlikely(pmd_bad(*pmd)))
+ return no_page_table(vma, flags);
+@@ -333,7 +344,7 @@ static struct page *follow_pmd_mask(stru
+ if (pmd_none(pmdval))
+ return no_page_table(vma, flags);
+ if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) {
+- page = follow_huge_pmd(mm, address, pmd, flags);
++ page = follow_huge_pmd_pte(vma, address, flags);
+ if (page)
+ return page;
+ return no_page_table(vma, flags);
+--- a/mm/hugetlb.c
++++ b/mm/hugetlb.c
+@@ -5157,30 +5157,30 @@ follow_huge_pd(struct vm_area_struct *vm
+ }
+
+ struct page * __weak
+-follow_huge_pmd(struct mm_struct *mm, unsigned long address,
+- pmd_t *pmd, int flags)
++follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address, int flags)
+ {
++ struct hstate *h = hstate_vma(vma);
++ struct mm_struct *mm = vma->vm_mm;
+ struct page *page = NULL;
+ spinlock_t *ptl;
+- pte_t pte;
++ pte_t *ptep, pte;
++
+ retry:
+- ptl = pmd_lockptr(mm, pmd);
+- spin_lock(ptl);
+- /*
+- * make sure that the address range covered by this pmd is not
+- * unmapped from other threads.
+- */
+- if (!pmd_huge(*pmd))
+- goto out;
+- pte = huge_ptep_get((pte_t *)pmd);
++ ptep = huge_pte_offset(mm, address, huge_page_size(h));
++ if (!ptep)
++ return NULL;
++
++ ptl = huge_pte_lock(h, mm, ptep);
++ pte = huge_ptep_get(ptep);
+ if (pte_present(pte)) {
+- page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
++ page = pte_page(pte) +
++ ((address & ~huge_page_mask(h)) >> PAGE_SHIFT);
+ if (flags & FOLL_GET)
+ get_page(page);
+ } else {
+ if (is_hugetlb_entry_migration(pte)) {
+ spin_unlock(ptl);
+- __migration_entry_wait(mm, (pte_t *)pmd, ptl);
++ __migration_entry_wait(mm, ptep, ptl);
+ goto retry;
+ }
+ /*
+@@ -5188,7 +5188,7 @@ retry:
+ * follow_page_mask().
+ */
+ }
+-out:
++
+ spin_unlock(ptl);
+ return page;
+ }
projects / thirdparty / kernel / stable-queue.git / commitdiff
