[RFC PATCH 07/15] usercopy: Don't assume the kernel stack size

[Mostafa Saleh <smostafa@google.com>]

check_stack_object() assumes that the kernel stack size is
THREAD_SIZE.

The allocated kernel stack size may not be THREAD_SIZE anymore, rely
on the newly introduced helper task_stack_{low, high}()

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 mm/usercopy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/usercopy.c b/mm/usercopy.c
index 5de7a518b1b1..f31a42b9f9c4 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -36,8 +36,8 @@
  */
 static noinline int check_stack_object(const void *obj, unsigned long len)
 {
-	const void * const stack = task_stack_page(current);
-	const void * const stackend = stack + THREAD_SIZE;
+	const void * const stack = task_stack_low(current);
+	const void * const stackend = task_stack_high(current);
 	int ret;
 
 	/* Object is not on the stack at all. */
-- 
2.56.0.rc1.315.gc6ed9934b7-goog