From: Baolin Wang baolin.wang@linux.alibaba.com

[ Upstream commit fac35ba763ed07ba93154c95ffc0c4a55023707f ]

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 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 --- v2: Fix up stray out label that is now unused.

include/linux/hugetlb.h | 6 +++--- mm/gup.c | 13 ++++++++++++- mm/hugetlb.c | 30 +++++++++++++++--------------- 3 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index cef70d6e1657..c7507135c2a0 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -127,8 +127,8 @@ 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, @@ -175,7 +175,7 @@ static inline void hugetlb_show_meminfo(void) { } #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) diff --git a/mm/gup.c b/mm/gup.c index 3ef769529548..98bd5e0a51c8 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -188,6 +188,17 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, 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(struct vm_area_struct *vma, 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); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2126d78f053d..e4478b62d0f7 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5157,30 +5157,30 @@ 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; + 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 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, * follow_page_mask(). */ } -out: + spin_unlock(ptl); return page; }