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mm: make stack guard page logic use vm_prev pointer 

Like the mlock() change previously, this makes the stack guard check
code use vma->vm_prev to see what the mapping below the current stack
is, rather than have to look it up with find_vma().

Also, accept an abutting stack segment, since that happens naturally if
you split the stack with mlock or mprotect.

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 16:49:40 -07:00
parent 7798330ac8
commit 0e8e50e20c
1 changed files with 11 additions and 4 deletions
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15
mm/memory.c
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@ -2770,11 +2770,18 @@ static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned lo
{
address &= PAGE_MASK;
if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
address -= PAGE_SIZE;
if (find_vma(vma->vm_mm, address) != vma)
return -ENOMEM;
struct vm_area_struct *prev = vma->vm_prev;
expand_stack(vma, address);
/*
* Is there a mapping abutting this one below?
*
* That's only ok if it's the same stack mapping
* that has gotten split..
*/
if (prev && prev->vm_end == address)
return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
expand_stack(vma, address - PAGE_SIZE);
}
return 0;
}