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| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2015-07-06 23:18:37 +0300 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2015-08-11 09:57:27 +0100 |
| commit | 9760c0f9a5a7dbfb696b799189609a3471151cb5 (patch) | |
| tree | 96b6afb47c3e57ac6b87c0bc8e10bf6f8d3edd16 /mm | |
| parent | 9bc34abfec8f083cb5ea50534d22d114ab12c4e3 (diff) | |
| download | lwn-9760c0f9a5a7dbfb696b799189609a3471151cb5.tar.gz lwn-9760c0f9a5a7dbfb696b799189609a3471151cb5.zip | |
mm: avoid setting up anonymous pages into file mapping
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>
[ luis: backported to 3.16: used Kirill's backport to 3.18 ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/mm/memory.c b/mm/memory.c index e7ae35a5ffeb..4e03447b1ef2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2637,6 +2637,10 @@ 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; @@ -3031,6 +3035,9 @@ 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; if (!(flags & FAULT_FLAG_WRITE)) return do_read_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); @@ -3191,11 +3198,10 @@ static 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); } |