From 176ba4c19d1bb153aa6baaa61d586e785b7d736c Mon Sep 17 00:00:00 2001 From: Baolin Wang Date: Thu, 1 Sep 2022 18:41:31 +0800 Subject: mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page 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 Suggested-by: Mike Kravetz Reviewed-by: Mike Kravetz Cc: David Hildenbrand Cc: Muchun Song Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin [5.4: Fixup contextual diffs before pin_user_pages()] Signed-off-by: Samuel Mendoza-Jonas Signed-off-by: Greg Kroah-Hartman --- include/linux/hugetlb.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/linux') 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) -- cgit v1.2.3