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77 lines
2.6 KiB
Diff
77 lines
2.6 KiB
Diff
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From 6b7339f4c31ad69c8e9c0b2859276e22cf72176d Mon Sep 17 00:00:00 2001
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
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Date: Mon, 6 Jul 2015 23:18:37 +0300
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Subject: mm: avoid setting up anonymous pages into file mapping
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Reading page fault handler code I've noticed that under right
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circumstances kernel would map anonymous pages into file mappings: if
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the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated
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on ->mmap(), kernel would handle page fault to not populated pte with
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do_anonymous_page().
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Let's change page fault handler to use do_anonymous_page() only on
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anonymous VMA (->vm_ops == NULL) and make sure that the VMA is not
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shared.
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For file mappings without vm_ops->fault() or shred VMA without vm_ops,
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page fault on pte_none() entry would lead to SIGBUS.
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Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
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Acked-by: Oleg Nesterov <oleg@redhat.com>
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Cc: Andrew Morton <akpm@linux-foundation.org>
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Cc: Willy Tarreau <w@1wt.eu>
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Cc: stable@vger.kernel.org
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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mm/memory.c | 20 +++++++++++++-------
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1 file changed, 13 insertions(+), 7 deletions(-)
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diff --git a/mm/memory.c b/mm/memory.c
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index a84fbb7..388dcf9 100644
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--- a/mm/memory.c
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+++ b/mm/memory.c
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@@ -2670,6 +2670,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
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pte_unmap(page_table);
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+ /* File mapping without ->vm_ops ? */
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+ if (vma->vm_flags & VM_SHARED)
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+ return VM_FAULT_SIGBUS;
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+
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/* Check if we need to add a guard page to the stack */
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if (check_stack_guard_page(vma, address) < 0)
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return VM_FAULT_SIGSEGV;
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@@ -3099,6 +3103,9 @@ static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
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- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
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pte_unmap(page_table);
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+ /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
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+ if (!vma->vm_ops->fault)
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+ return VM_FAULT_SIGBUS;
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if (!(flags & FAULT_FLAG_WRITE))
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return do_read_fault(mm, vma, address, pmd, pgoff, flags,
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orig_pte);
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@@ -3244,13 +3251,12 @@ static int handle_pte_fault(struct mm_struct *mm,
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barrier();
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if (!pte_present(entry)) {
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if (pte_none(entry)) {
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- if (vma->vm_ops) {
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- if (likely(vma->vm_ops->fault))
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- return do_fault(mm, vma, address, pte,
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- pmd, flags, entry);
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- }
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- return do_anonymous_page(mm, vma, address,
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- pte, pmd, flags);
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+ if (vma->vm_ops)
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+ return do_fault(mm, vma, address, pte, pmd,
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+ flags, entry);
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+
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+ return do_anonymous_page(mm, vma, address, pte, pmd,
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+ flags);
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}
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return do_swap_page(mm, vma, address,
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pte, pmd, flags, entry);
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--
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cgit v1.1
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