diff options
| author | Kirill A. Shutemov | 2015-07-06 23:18:37 +0300 |
|---|---|---|
| committer | Linus Torvalds | 2015-07-09 11:12:48 -0700 |
| commit | 6b7339f4c31ad69c8e9c0b2859276e22cf72176d (patch) | |
| tree | ee208aa15f03b4c7336e56d6767dfecb87be9d7b | |
| parent | 883a2dfd6f13eca5aab30f0bcc9a6f1e2f983b1e (diff) | |
mm: avoid setting up anonymous pages into file mapping
Reading page fault handler code I've noticed that under right
circumstances kernel would map anonymous pages into file mappings: if
the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated
on ->mmap(), kernel would handle page fault to not populated pte with
do_anonymous_page().
Let's change page fault handler to use do_anonymous_page() only on
anonymous VMA (->vm_ops == NULL) and make sure that the VMA is not
shared.
For file mappings without vm_ops->fault() or shred VMA without vm_ops,
page fault on pte_none() entry would lead to SIGBUS.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Willy Tarreau <w@1wt.eu>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/memory.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/mm/memory.c b/mm/memory.c index a84fbb772034..388dcf9aa283 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2670,6 +2670,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap(page_table); + /* File mapping without ->vm_ops ? */ + if (vma->vm_flags & VM_SHARED) + return VM_FAULT_SIGBUS; + /* Check if we need to add a guard page to the stack */ if (check_stack_guard_page(vma, address) < 0) return VM_FAULT_SIGSEGV; @@ -3099,6 +3103,9 @@ static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma, - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; pte_unmap(page_table); + /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */ + if (!vma->vm_ops->fault) + return VM_FAULT_SIGBUS; if (!(flags & FAULT_FLAG_WRITE)) return do_read_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); @@ -3244,13 +3251,12 @@ static int handle_pte_fault(struct mm_struct *mm, barrier(); if (!pte_present(entry)) { if (pte_none(entry)) { - if (vma->vm_ops) { - if (likely(vma->vm_ops->fault)) - return do_fault(mm, vma, address, pte, - pmd, flags, entry); - } - return do_anonymous_page(mm, vma, address, - pte, pmd, flags); + if (vma->vm_ops) + return do_fault(mm, vma, address, pte, pmd, + flags, entry); + + return do_anonymous_page(mm, vma, address, pte, pmd, + flags); } return do_swap_page(mm, vma, address, pte, pmd, flags, entry); |