diff options
Diffstat (limited to 'mm/mprotect.c')
| -rw-r--r-- | mm/mprotect.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c index 86a28c0e190f..72aabffb7871 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -44,8 +44,10 @@ static inline bool can_change_pte_writable(struct vm_area_struct *vma, { struct page *page; - VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte)); + if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) + return false; + /* Don't touch entries that are not even readable. */ if (pte_protnone(pte)) return false; @@ -59,15 +61,22 @@ static inline bool can_change_pte_writable(struct vm_area_struct *vma, if (!(vma->vm_flags & VM_SHARED)) { /* - * We can only special-case on exclusive anonymous pages, - * because we know that our write-fault handler similarly would - * map them writable without any additional checks while holding - * the PT lock. + * Writable MAP_PRIVATE mapping: We can only special-case on + * exclusive anonymous pages, because we know that our + * write-fault handler similarly would map them writable without + * any additional checks while holding the PT lock. */ page = vm_normal_page(vma, addr, pte); return page && PageAnon(page) && PageAnonExclusive(page); } + /* + * Writable MAP_SHARED mapping: "clean" might indicate that the FS still + * needs a real write-fault for writenotify + * (see vma_wants_writenotify()). If "dirty", the assumption is that the + * FS was already notified and we can simply mark the PTE writable + * just like the write-fault handler would do. + */ return pte_dirty(pte); } |