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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>
This commit is contained in:
Linus Torvalds 2010-08-20 16:39:25 -07:00
parent 297c5eee37
commit 7798330ac8
1 changed files with 16 additions and 5 deletions
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21
mm/mlock.c
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@ -135,6 +135,19 @@ void munlock_vma_page(struct page *page)
}
}
/* Is the vma a continuation of the stack vma above it? */
static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)
{
return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
}
static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
{
return (vma->vm_flags & VM_GROWSDOWN) &&
(vma->vm_start == addr) &&
!vma_stack_continue(vma->vm_prev, addr);
}
/**
* __mlock_vma_pages_range() - mlock a range of pages in the vma.
* @vma: target vma
@ -168,11 +181,9 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
gup_flags |= FOLL_WRITE;
/* We don't try to access the guard page of a stack vma */
if (vma->vm_flags & VM_GROWSDOWN) {
if (start == vma->vm_start) {
start += PAGE_SIZE;
nr_pages--;
}
if (stack_guard_page(vma, start)) {
addr += PAGE_SIZE;
nr_pages--;
}
while (nr_pages > 0) {