diff options
| -rw-r--r-- | mm/mmap.c | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 37a1fcac029d..2664a47cec93 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2185,9 +2185,28 @@ int expand_downwards(struct vm_area_struct *vma, return error; } +/* + * Note how expand_stack() refuses to expand the stack all the way to + * abut the next virtual mapping, *unless* that mapping itself is also + * a stack mapping. We want to leave room for a guard page, after all + * (the guard page itself is not added here, that is done by the + * actual page faulting logic) + * + * This matches the behavior of the guard page logic (see mm/memory.c: + * check_stack_guard_page()), which only allows the guard page to be + * removed under these circumstances. + */ #ifdef CONFIG_STACK_GROWSUP int expand_stack(struct vm_area_struct *vma, unsigned long address) { + struct vm_area_struct *next; + + address &= PAGE_MASK; + next = vma->vm_next; + if (next && next->vm_start == address + PAGE_SIZE) { + if (!(next->vm_flags & VM_GROWSUP)) + return -ENOMEM; + } return expand_upwards(vma, address); } @@ -2209,6 +2228,14 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr) #else int expand_stack(struct vm_area_struct *vma, unsigned long address) { + struct vm_area_struct *prev; + + address &= PAGE_MASK; + prev = vma->vm_prev; + if (prev && prev->vm_end == address) { + if (!(prev->vm_flags & VM_GROWSDOWN)) + return -ENOMEM; + } return expand_downwards(vma, address); } |