From: Dev Jain Date: Wed, 6 Aug 2025 14:56:11 +0000 (+0530) Subject: mm: pass page directly instead of using folio_page X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=cf1b80dc31a1137b8b4568c138b453bf7453204a;p=users%2Fjedix%2Flinux-maple.git mm: pass page directly instead of using folio_page In commit_anon_folio_batch(), we iterate over all pages pointed to by the PTE batch. Therefore we need to know the first page of the batch; currently we derive that via folio_page(folio, 0), but, that takes us to the first (head) page of the folio instead - our PTE batch may lie in the middle of the folio, leading to incorrectness. Bite the bullet and throw away the micro-optimization of reusing the folio in favour of code simplicity. Derive the page and the folio in change_pte_range, and pass the page too to commit_anon_folio_batch to fix the aforementioned issue. Link: https://lkml.kernel.org/r/20250806145611.3962-1-dev.jain@arm.com Fixes: cac1db8c3aad ("mm: optimize mprotect() by PTE batching") Reported-by: syzbot+57bcc752f0df8bb1365c@syzkaller.appspotmail.com Signed-off-by: Dev Jain Reviewed-by: Lorenzo Stoakes Debugged-by: David Hildenbrand Acked-by: David Hildenbrand Cc: Anshuman Khandual Cc: Barry Song Cc: Catalin Marinas Cc: Christophe Leroy Cc: Hugh Dickins Cc: Jann Horn Cc: Joey Gouly Cc: Kevin Brodsky Cc: Lance Yang Cc: Liam Howlett Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Ryan Roberts Cc: Vlastimil Babka Cc: Will Deacon Cc: Yang Shi Cc: Yicong Yang Cc: Zhenhua Huang Cc: Zi Yan Signed-off-by: Andrew Morton --- diff --git a/mm/mprotect.c b/mm/mprotect.c index 78bded7acf79..113b48985834 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -120,9 +120,8 @@ static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep, static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, pte_t oldpte, pte_t *pte, int target_node, - struct folio **foliop) + struct folio *folio) { - struct folio *folio = NULL; bool ret = true; bool toptier; int nid; @@ -131,7 +130,6 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, if (pte_protnone(oldpte)) goto skip; - folio = vm_normal_folio(vma, addr, oldpte); if (!folio) goto skip; @@ -173,7 +171,6 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, folio_xchg_access_time(folio, jiffies_to_msecs(jiffies)); skip: - *foliop = folio; return ret; } @@ -231,10 +228,9 @@ static int page_anon_exclusive_sub_batch(int start_idx, int max_len, * retrieve sub-batches. */ static void commit_anon_folio_batch(struct vm_area_struct *vma, - struct folio *folio, unsigned long addr, pte_t *ptep, + struct folio *folio, struct page *first_page, unsigned long addr, pte_t *ptep, pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) { - struct page *first_page = folio_page(folio, 0); bool expected_anon_exclusive; int sub_batch_idx = 0; int len; @@ -251,7 +247,7 @@ static void commit_anon_folio_batch(struct vm_area_struct *vma, } static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, - struct folio *folio, unsigned long addr, pte_t *ptep, + struct folio *folio, struct page *page, unsigned long addr, pte_t *ptep, pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) { bool set_write; @@ -270,7 +266,7 @@ static void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, /* idx = */ 0, set_write, tlb); return; } - commit_anon_folio_batch(vma, folio, addr, ptep, oldpte, ptent, nr_ptes, tlb); + commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb); } static long change_pte_range(struct mmu_gather *tlb, @@ -305,15 +301,19 @@ static long change_pte_range(struct mmu_gather *tlb, const fpb_t flags = FPB_RESPECT_SOFT_DIRTY | FPB_RESPECT_WRITE; int max_nr_ptes = (end - addr) >> PAGE_SHIFT; struct folio *folio = NULL; + struct page *page; pte_t ptent; + page = vm_normal_page(vma, addr, oldpte); + if (page) + folio = page_folio(page); /* * Avoid trapping faults against the zero or KSM * pages. See similar comment in change_huge_pmd. */ if (prot_numa) { int ret = prot_numa_skip(vma, addr, oldpte, pte, - target_node, &folio); + target_node, folio); if (ret) { /* determine batch to skip */ @@ -323,9 +323,6 @@ static long change_pte_range(struct mmu_gather *tlb, } } - if (!folio) - folio = vm_normal_folio(vma, addr, oldpte); - nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags); oldpte = modify_prot_start_ptes(vma, addr, pte, nr_ptes); @@ -351,7 +348,7 @@ static long change_pte_range(struct mmu_gather *tlb, */ if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pte_write(ptent)) - set_write_prot_commit_flush_ptes(vma, folio, + set_write_prot_commit_flush_ptes(vma, folio, page, addr, pte, oldpte, ptent, nr_ptes, tlb); else prot_commit_flush_ptes(vma, addr, pte, oldpte, ptent,