The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
fac35ba763ed ("mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page") ad1ac596e8a8 ("mm/migration: fix potential pte_unmap on an not mapped pte") 4dd845b5a3e5 ("mm/swapops: rework swap entry manipulation code") af5cdaf82238 ("mm: remove special swap entry functions") b3807a91aca7 ("mm: page_vma_mapped_walk(): add a level of indentation") e2e1d4076c77 ("mm: page_vma_mapped_walk(): prettify PVMW_MIGRATION block") 3306d3119cea ("mm: page_vma_mapped_walk(): use pmde for *pvmw->pmd") f003c03bd29e ("mm: page_vma_mapped_walk(): use page for pvmw->page") 494334e43c16 ("mm/thp: fix vma_address() if virtual address below file offset") 732ed55823fc ("mm/thp: try_to_unmap() use TTU_SYNC for safe splitting") 99fa8a48203d ("mm/thp: fix __split_huge_pmd_locked() on shmem migration entry") ffc90cbb2970 ("mm, thp: use head page in __migration_entry_wait()") a44f89dc6c5f ("mm/huge_memory.c: use helper function migration_entry_to_page()") 374437a274e2 ("mm/pgtable-generic.c: optimize the VM_BUG_ON condition in pmdp_huge_clear_flush()") c045c72ccde3 ("mm/pgtable-generic.c: simplify the VM_BUG_ON condition in pmdp_huge_clear_flush()") 013339df116c ("mm/rmap: always do TTU_IGNORE_ACCESS") 336bf30eb765 ("hugetlbfs: fix anon huge page migration race") df3a57d1f607 ("mm: split out the non-present case from copy_one_pte()") ec0abae6dcdf ("mm/thp: fix __split_huge_pmd_locked() for migration PMD") 6128763fc324 ("mm/migrate: remove unnecessary is_zone_device_page() check")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
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: [PATCH] mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page
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/635f43bdd85ac2615a58405da82b4d33c6e5eb05.166201756... 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
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 3ec981a0d8b3..67c88b82fc32 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -207,8 +207,8 @@ struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, 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, @@ -312,8 +312,8 @@ static inline struct page *follow_huge_pd(struct vm_area_struct *vma, return NULL; }
-static inline struct page *follow_huge_pmd(struct mm_struct *mm, - unsigned long address, pmd_t *pmd, int flags) +static inline struct page *follow_huge_pmd_pte(struct vm_area_struct *vma, + unsigned long address, int flags) { return NULL; } diff --git a/mm/gup.c b/mm/gup.c index 00926abb4426..251cb6a10bc0 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -530,6 +530,18 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == (FOLL_PIN | FOLL_GET))) return ERR_PTR(-EINVAL); + + /* + * 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); @@ -662,7 +674,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, if (pmd_none(pmdval)) return no_page_table(vma, flags); if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) { - 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); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 0bdfc7e1c933..9564bf817e6a 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6946,12 +6946,13 @@ follow_huge_pd(struct vm_area_struct *vma, }
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;
/* * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via @@ -6961,17 +6962,15 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, return NULL;
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); /* * try_grab_page() should always succeed here, because: a) we * hold the pmd (ptl) lock, and b) we've just checked that the @@ -6987,7 +6986,7 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, } else { if (is_hugetlb_entry_migration(pte)) { spin_unlock(ptl); - __migration_entry_wait_huge((pte_t *)pmd, ptl); + __migration_entry_wait_huge(ptep, ptl); goto retry; } /*