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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2015-07-06 23:18:37 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-07-09 11:12:48 -0700
commit6b7339f4c31ad69c8e9c0b2859276e22cf72176d (patch)
treeee208aa15f03b4c7336e56d6767dfecb87be9d7b
parent883a2dfd6f13eca5aab30f0bcc9a6f1e2f983b1e (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.c20
1 files changed, 13 insertions, 7 deletions
diff --git a/mm/memory.c b/mm/memory.c
index a84fbb7..388dcf9 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);