diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/huge_memory.c | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7ab9a171e3d0..2a73efea02d7 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1583,6 +1583,24 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pgtable_t pgtable = NULL; int ret = -ENOMEM; + pmd = pmdp_get_lockless(src_pmd); + if (unlikely(pmd_special(pmd))) { + dst_ptl = pmd_lock(dst_mm, dst_pmd); + src_ptl = pmd_lockptr(src_mm, src_pmd); + spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); + /* + * No need to recheck the pmd, it can't change with write + * mmap lock held here. + * + * Meanwhile, making sure it's not a CoW VMA with writable + * mapping, otherwise it means either the anon page wrongly + * applied special bit, or we made the PRIVATE mapping be + * able to wrongly write to the backend MMIO. + */ + VM_WARN_ON_ONCE(is_cow_mapping(src_vma->vm_flags) && pmd_write(pmd)); + goto set_pmd; + } + /* Skip if can be re-fill on fault */ if (!vma_is_anonymous(dst_vma)) return 0; @@ -1664,7 +1682,9 @@ out_zero_page: pmdp_set_wrprotect(src_mm, addr, src_pmd); if (!userfaultfd_wp(dst_vma)) pmd = pmd_clear_uffd_wp(pmd); - pmd = pmd_mkold(pmd_wrprotect(pmd)); + pmd = pmd_wrprotect(pmd); +set_pmd: + pmd = pmd_mkold(pmd); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; @@ -1710,8 +1730,11 @@ int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, * TODO: once we support anonymous pages, use * folio_try_dup_anon_rmap_*() and split if duplicating fails. */ - pudp_set_wrprotect(src_mm, addr, src_pud); - pud = pud_mkold(pud_wrprotect(pud)); + if (is_cow_mapping(vma->vm_flags) && pud_write(pud)) { + pudp_set_wrprotect(src_mm, addr, src_pud); + pud = pud_wrprotect(pud); + } + pud = pud_mkold(pud); set_pud_at(dst_mm, addr, dst_pud, pud); ret = 0; |