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charset="utf-8" From: "Liam R. Howlett" Instead of zeroing the vma tree and then overwriting the area, let the area be overwritten and then clean up the gathered vmas using vms_complete_munmap_vmas(). If a driver is mapping over an existing vma, then clear the ptes before the call_mmap() invocation. This is done using the vms_clear_ptes() helper. Temporarily keep track of the number of pages that will be removed and reduce the charged amount. This also drops the validate_mm() call in the vma_expand() function. It is necessary to drop the validate as it would fail since the mm map_count would be incorrect during a vma expansion, prior to the cleanup from vms_complete_munmap_vmas(). Clean up the error handing of the vms_gather_munmap_vmas() by calling the verification within the function. Signed-off-by: Liam R. Howlett Reviewed-by: Lorenzo Stoakes --- mm/internal.h | 1 + mm/mmap.c | 80 +++++++++++++++++++++++++++------------------------ 2 files changed, 44 insertions(+), 37 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 11e90c6e5a3e..dd4eede1be0f 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1503,6 +1503,7 @@ struct vma_munmap_struct { unsigned long stack_vm; unsigned long data_vm; bool unlock; /* Unlock after the munmap */ + bool clear_ptes; /* If there are outstanding PTE to be cleared */ }; =20 void __meminit __init_single_page(struct page *page, unsigned long pfn, diff --git a/mm/mmap.c b/mm/mmap.c index 870c2d04ad6b..58cf42e22bfe 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -401,17 +401,21 @@ anon_vma_interval_tree_post_update_vma(struct vm_area= _struct *vma) } =20 static unsigned long count_vma_pages_range(struct mm_struct *mm, - unsigned long addr, unsigned long end) + unsigned long addr, unsigned long end, + unsigned long *nr_accounted) { VMA_ITERATOR(vmi, mm, addr); struct vm_area_struct *vma; unsigned long nr_pages =3D 0; =20 + *nr_accounted =3D 0; for_each_vma_range(vmi, vma, end) { unsigned long vm_start =3D max(addr, vma->vm_start); unsigned long vm_end =3D min(end, vma->vm_end); =20 nr_pages +=3D PHYS_PFN(vm_end - vm_start); + if (vma->vm_flags & VM_ACCOUNT) + *nr_accounted +=3D PHYS_PFN(vm_end - vm_start); } =20 return nr_pages; @@ -524,6 +528,7 @@ static inline void init_vma_munmap(struct vma_munmap_st= ruct *vms, vms->exec_vm =3D vms->stack_vm =3D vms->data_vm =3D 0; vms->unmap_start =3D FIRST_USER_ADDRESS; vms->unmap_end =3D USER_PGTABLES_CEILING; + vms->clear_ptes =3D false; /* No PTEs to clear yet */ } =20 /* @@ -732,7 +737,6 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area= _struct *vma, vma_iter_store(vmi, vma); =20 vma_complete(&vp, vmi, vma->vm_mm); - validate_mm(vma->vm_mm); return 0; =20 nomem: @@ -2606,11 +2610,14 @@ static inline void abort_munmap_vmas(struct ma_stat= e *mas_detach) } =20 =20 -static void vms_complete_pte_clear(struct vma_munmap_struct *vms, +static inline void vms_clear_ptes(struct vma_munmap_struct *vms, struct ma_state *mas_detach, bool mm_wr_locked) { struct mmu_gather tlb; =20 + if (!vms->clear_ptes) /* Nothing to do */ + return; + /* * We can free page tables without write-locking mmap_lock because VMAs * were isolated before we downgraded mmap_lock. @@ -2624,6 +2631,7 @@ static void vms_complete_pte_clear(struct vma_munmap_= struct *vms, /* start and end may be different if there is no prev or next vma. */ free_pgtables(&tlb, mas_detach, vms->vma, vms->unmap_start, vms->unmap_en= d, mm_wr_locked); tlb_finish_mmu(&tlb); + vms->clear_ptes =3D false; } =20 /* @@ -2647,7 +2655,7 @@ static void vms_complete_munmap_vmas(struct vma_munma= p_struct *vms, if (vms->unlock) mmap_write_downgrade(mm); =20 - vms_complete_pte_clear(vms, mas_detach, !vms->unlock); + vms_clear_ptes(vms, mas_detach, !vms->unlock); /* Update high watermark before we lower total_vm */ update_hiwater_vm(mm); /* Stat accounting */ @@ -2799,6 +2807,9 @@ static int vms_gather_munmap_vmas(struct vma_munmap_s= truct *vms, while (vma_iter_addr(vms->vmi) > vms->start) vma_iter_prev_range(vms->vmi); =20 + /* There are now PTEs that need to be cleared */ + vms->clear_ptes =3D true; + return 0; =20 userfaultfd_error: @@ -2807,6 +2818,7 @@ static int vms_gather_munmap_vmas(struct vma_munmap_s= truct *vms, abort_munmap_vmas(mas_detach); start_split_failed: map_count_exceeded: + validate_mm(vms->mm); return error; } =20 @@ -2851,8 +2863,8 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct = vm_area_struct *vma, =20 clear_tree_failed: abort_munmap_vmas(&mas_detach); -gather_failed: validate_mm(mm); +gather_failed: return error; } =20 @@ -2940,24 +2952,19 @@ unsigned long mmap_region(struct file *file, unsign= ed long addr, unsigned long merge_start =3D addr, merge_end =3D end; bool writable_file_mapping =3D false; pgoff_t vm_pgoff; - int error; + int error =3D -ENOMEM; VMA_ITERATOR(vmi, mm, addr); + unsigned long nr_pages, nr_accounted; =20 - /* Check against address space limit. */ - if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) { - unsigned long nr_pages; - - /* - * MAP_FIXED may remove pages of mappings that intersects with - * requested mapping. Account for the pages it would unmap. - */ - nr_pages =3D count_vma_pages_range(mm, addr, end); - - if (!may_expand_vm(mm, vm_flags, - (len >> PAGE_SHIFT) - nr_pages)) - return -ENOMEM; - } + nr_pages =3D count_vma_pages_range(mm, addr, end, &nr_accounted); =20 + /* + * Check against address space limit. + * MAP_FIXED may remove pages of mappings that intersects with requested + * mapping. Account for the pages it would unmap. + */ + if (!may_expand_vm(mm, vm_flags, (len >> PAGE_SHIFT) - nr_pages)) + return -ENOMEM; =20 if (unlikely(!can_modify_mm(mm, addr, end))) return -EPERM; @@ -2974,18 +2981,13 @@ unsigned long mmap_region(struct file *file, unsign= ed long addr, mas_init(&mas_detach, &mt_detach, /* addr =3D */ 0); /* Prepare to unmap any existing mapping in the area */ if (vms_gather_munmap_vmas(&vms, &mas_detach)) - goto gather_failed; - - /* Remove any existing mappings from the vma tree */ - if (vma_iter_clear_gfp(&vmi, addr, end, GFP_KERNEL)) - goto clear_tree_failed; + return -ENOMEM; =20 - /* Unmap any existing mapping in the area */ - vms_complete_munmap_vmas(&vms, &mas_detach); next =3D vms.next; prev =3D vms.prev; vma =3D NULL; } else { + /* Minimal setup of vms */ next =3D vma_next(&vmi); prev =3D vma_prev(&vmi); if (prev) @@ -2997,8 +2999,10 @@ unsigned long mmap_region(struct file *file, unsigne= d long addr, */ if (accountable_mapping(file, vm_flags)) { charged =3D len >> PAGE_SHIFT; + charged -=3D nr_accounted; if (security_vm_enough_memory_mm(mm, charged)) - return -ENOMEM; + goto abort_munmap; + vms.nr_accounted =3D 0; vm_flags |=3D VM_ACCOUNT; } =20 @@ -3047,10 +3051,8 @@ unsigned long mmap_region(struct file *file, unsigne= d long addr, * not unmapped, but the maps are removed from the list. */ vma =3D vm_area_alloc(mm); - if (!vma) { - error =3D -ENOMEM; + if (!vma) goto unacct_error; - } =20 vma_iter_config(&vmi, addr, end); vma_set_range(vma, addr, end, pgoff); @@ -3059,6 +3061,8 @@ unsigned long mmap_region(struct file *file, unsigned= long addr, =20 if (file) { vma->vm_file =3D get_file(file); + /* call_mmap() may map PTE, so ensure there are no existing PTEs */ + vms_clear_ptes(&vms, &mas_detach, true); error =3D call_mmap(file, vma); if (error) goto unmap_and_free_vma; @@ -3149,6 +3153,10 @@ unsigned long mmap_region(struct file *file, unsigne= d long addr, expanded: perf_event_mmap(vma); =20 + /* Unmap any existing mapping in the area */ + if (vms.nr_pages) + vms_complete_munmap_vmas(&vms, &mas_detach); + vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT); if (vm_flags & VM_LOCKED) { if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) || @@ -3196,14 +3204,12 @@ unsigned long mmap_region(struct file *file, unsign= ed long addr, unacct_error: if (charged) vm_unacct_memory(charged); - validate_mm(mm); - return error; =20 -clear_tree_failed: - abort_munmap_vmas(&mas_detach); -gather_failed: +abort_munmap: + if (vms.nr_pages) + abort_munmap_vmas(&mas_detach); validate_mm(mm); - return -ENOMEM; + return error; } =20 static int __vm_munmap(unsigned long start, size_t len, bool unlock) --=20 2.43.0