mm: make the mlock() stack guard page checks stricter
If we've split the stack vma, only the lowest one has the guard page. Now that we have a doubly linked list of vma's, checking this is trivial. Tested-by: Ian Campbell <ijc@hellion.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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297c5eee37
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19
mm/mlock.c
19
mm/mlock.c
@ -135,6 +135,19 @@ void munlock_vma_page(struct page *page)
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}
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}
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/* Is the vma a continuation of the stack vma above it? */
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static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)
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{
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return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
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}
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static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
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{
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return (vma->vm_flags & VM_GROWSDOWN) &&
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(vma->vm_start == addr) &&
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!vma_stack_continue(vma->vm_prev, addr);
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}
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/**
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* __mlock_vma_pages_range() - mlock a range of pages in the vma.
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* @vma: target vma
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@ -168,12 +181,10 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
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gup_flags |= FOLL_WRITE;
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/* We don't try to access the guard page of a stack vma */
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if (vma->vm_flags & VM_GROWSDOWN) {
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if (start == vma->vm_start) {
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start += PAGE_SIZE;
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if (stack_guard_page(vma, start)) {
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addr += PAGE_SIZE;
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nr_pages--;
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}
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}
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while (nr_pages > 0) {
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int i;
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