ARM: prevent VM_GROWSDOWN mmaps extending below FIRST_USER_ADDRESS
Cc: <stable@vger.kernel.org>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index f074675..5bb4835 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -247,7 +247,9 @@
return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags);
check_stack:
- if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
+ /* Don't allow expansion below FIRST_USER_ADDRESS */
+ if (vma->vm_flags & VM_GROWSDOWN &&
+ addr >= FIRST_USER_ADDRESS && !expand_stack(vma, addr))
goto good_area;
out:
return fault;