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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2015-07-06 23:18:37 +0300
committerWilly Tarreau <w@1wt.eu>2015-09-18 13:52:16 +0200
commitf85457f8be43e6fb2796d4728cc01806415acc51 (patch)
treec6545325b17b320e9bb6f4ab38b7c4cb0f31d7d3
parent9e5594d2355aa943785206cb7634826f77547253 (diff)
downloadlinux-linaro-stable-f85457f8be43e6fb2796d4728cc01806415acc51.tar.gz
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> [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>
-rw-r--r--mm/memory.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 085b06888245..e36dee273de4 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);
}