From fac35ba763ed07ba93154c95ffc0c4a55023707f 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 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 --- mm/gup.c | 14 +++++++++++++- mm/hugetlb.c | 27 +++++++++++++-------------- 2 files changed, 26 insertions(+), 15 deletions(-) (limited to 'mm') 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 @@ retry: } 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; } /* -- cgit v1.2.3 From b1f44cdabad8c50cd72d6b6731e9fdf3730a8f4f Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Sun, 2 Oct 2022 19:31:30 +0000 Subject: mm/damon/core: initialize damon_target->list in damon_new_target() 'struct damon_target' creation function, 'damon_new_target()' is not initializing its '->list' field, unlike other DAMON structs creator functions such as 'damon_new_region()'. Normal users of 'damon_new_target()' initializes the field by adding the target to DAMON context's targets list, but some code could access the uninitialized field. This commit avoids the case by initializing the field in 'damon_new_target()'. Link: https://lkml.kernel.org/r/20221002193130.8227-1-sj@kernel.org Fixes: f23b8eee1871 ("mm/damon/core: implement region-based sampling") Signed-off-by: SeongJae Park Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: Andrew Morton --- mm/damon/core.c | 1 + 1 file changed, 1 insertion(+) (limited to 'mm') diff --git a/mm/damon/core.c b/mm/damon/core.c index 7d25dc582fe3..4cbe7867b547 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -313,6 +313,7 @@ struct damon_target *damon_new_target(void) t->pid = NULL; t->nr_regions = 0; INIT_LIST_HEAD(&t->regions_list); + INIT_LIST_HEAD(&t->list); return t; } -- cgit v1.2.3