Messages in this thread Patch in this message | | | Date | Sun, 13 Sep 2015 00:57:00 +0200 | From | Willy Tarreau <> | Subject | [PATCH 2.6.32 54/62] mm: avoid setting up anonymous pages into file mapping |
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2.6.32-longterm review patch. If anyone has any objections, please let me know.
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
commit 6b7339f4c31ad69c8e9c0b2859276e22cf72176d upstream.
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> (cherry picked from commit e2506476534cff7bb3697fbe0654fdefd101bc80)
Signed-off-by: Willy Tarreau <w@1wt.eu> --- mm/memory.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c index 085b068..e36dee2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2727,6 +2727,10 @@ 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_SIGBUS; @@ -2979,6 +2983,9 @@ static int do_linear_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; return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); } @@ -3037,11 +3044,9 @@ static inline int handle_pte_fault(struct mm_struct *mm, entry = *pte; if (!pte_present(entry)) { if (pte_none(entry)) { - if (vma->vm_ops) { - if (likely(vma->vm_ops->fault)) - return do_linear_fault(mm, vma, address, + if (vma->vm_ops) + return do_linear_fault(mm, vma, address, pte, pmd, flags, entry); - } return do_anonymous_page(mm, vma, address, pte, pmd, flags); } -- 1.7.12.2.21.g234cd45.dirty
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