[RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs

Yu-cheng Yu
2018-09-21T15:11:45Z

Create a guard area between VMAs, to detect memory corruption.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
include/linux/mm.h | 30 ++++++++++++++++++++----------
1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c4cc07baccda..3a823bdae09d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2443,24 +2443,34 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m
static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
{
unsigned long vm_start = vma->vm_start;
+ unsigned long gap;
+
+ if (vma->vm_flags & VM_GROWSDOWN)
+ gap = stack_guard_gap;
+ else
+ gap = PAGE_SIZE;
+
+ vm_start -= gap;
+ if (vm_start > vma->vm_start)
+ vm_start = 0;

- if (vma->vm_flags & VM_GROWSDOWN) {
- vm_start -= stack_guard_gap;
- if (vm_start > vma->vm_start)
- vm_start = 0;
- }
return vm_start;
}

static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
{
unsigned long vm_end = vma->vm_end;
+ unsigned long gap;
+
+ if (vma->vm_flags & VM_GROWSUP)
+ gap = stack_guard_gap;
+ else
+ gap = PAGE_SIZE;
+
+ vm_end += gap;
+ if (vm_end < vma->vm_end)
+ vm_end = -PAGE_SIZE;

- if (vma->vm_flags & VM_GROWSUP) {
- vm_end += stack_guard_gap;
- if (vm_end < vma->vm_end)
- vm_end = -PAGE_SIZE;
- }
return vm_end;
}

--
2.17.1