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Subject[PATCH v5 07/27] mm/mmap: Create a guard area between VMAs
Date
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 ++++++++++++++++++++----------
mm/Kconfig | 7 +++++++
2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0416a7204be3..53cfc104c0fb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2417,24 +2417,34 @@ 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 = 0;
+
+ if (vma->vm_flags & VM_GROWSDOWN)
+ gap = stack_guard_gap;
+ else if (IS_ENABLED(CONFIG_VM_AREA_GUARD))
+ 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 = 0;
+
+ if (vma->vm_flags & VM_GROWSUP)
+ gap = stack_guard_gap;
+ else if (IS_ENABLED(CONFIG_VM_AREA_GUARD))
+ 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;
}

diff --git a/mm/Kconfig b/mm/Kconfig
index de64ea658716..0cdcad65640d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -764,4 +764,11 @@ config GUP_BENCHMARK
config ARCH_HAS_PTE_SPECIAL
bool

+config VM_AREA_GUARD
+ bool "VM area guard"
+ default n
+ help
+ Create a guard area between VM areas so that access beyond
+ limit can be detected.
+
endmenu
--
2.17.1
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