diff options
| -rw-r--r-- | mm/memory.c | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/mm/memory.c b/mm/memory.c index 0bccc622e482..e8bfdf0d9d1d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2257,7 +2257,7 @@ static inline bool cow_user_page(struct page *dst, struct page *src, bool ret; void *kaddr; void __user *uaddr; - bool force_mkyoung; + bool locked = false; struct vm_area_struct *vma = vmf->vma; struct mm_struct *mm = vma->vm_mm; unsigned long addr = vmf->address; @@ -2282,11 +2282,11 @@ static inline bool cow_user_page(struct page *dst, struct page *src, * On architectures with software "accessed" bits, we would * take a double page fault, so mark it accessed here. */ - force_mkyoung = arch_faults_on_old_pte() && !pte_young(vmf->orig_pte); - if (force_mkyoung) { + if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) { pte_t entry; vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl); + locked = true; if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) { /* * Other thread has already handled the fault @@ -2310,18 +2310,37 @@ static inline bool cow_user_page(struct page *dst, struct page *src, * zeroes. */ if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { + if (locked) + goto warn; + + /* Re-validate under PTL if the page is still mapped */ + vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl); + locked = true; + if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) { + /* The PTE changed under us. Retry page fault. */ + ret = false; + goto pte_unlock; + } + /* - * Give a warn in case there can be some obscure - * use-case + * The same page can be mapped back since last copy attampt. + * Try to copy again under PTL. */ - WARN_ON_ONCE(1); - clear_page(kaddr); + if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { + /* + * Give a warn in case there can be some obscure + * use-case + */ +warn: + WARN_ON_ONCE(1); + clear_page(kaddr); + } } ret = true; pte_unlock: - if (force_mkyoung) + if (locked) pte_unmap_unlock(vmf->pte, vmf->ptl); kunmap_atomic(kaddr); flush_dcache_page(dst); |