From 7ddb5ec3fdd06d769f58a4d68fa4c3f7de26f2fb Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 20 Aug 2010 16:49:40 -0700 Subject: [PATCH] mm: make stack guard page logic use vm_prev pointer 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 Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index e48eb86cb6f..47fb0a0d349 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2761,11 +2761,18 @@ 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; + + /* + * 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); + expand_stack(vma, address - PAGE_SIZE); } return 0; } -- 2.11.4.GIT