Messages in this thread Patch in this message | | | Date | Tue, 24 Aug 2010 15:44:59 -0700 | From | Greg KH <> | Subject | [054/114] mm: make stack guard page logic use vm_prev pointer |
| |
2.6.35-stable review patch. If anyone has any objections, please let us know.
------------------
From: Linus Torvalds <torvalds@linux-foundation.org>
commit 0e8e50e20c837eeec8323bba7dcd25fe5479194c upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- mm/memory.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
--- a/mm/memory.c +++ b/mm/memory.c @@ -2770,11 +2770,18 @@ static inline int check_stack_guard_page { 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; }
| |