[RFC PATCH 07/15] usercopy: Don't assume the kernel stack size
From: Mostafa Saleh <smostafa@google.com>
Date: 2026-09-28 17:41:57
Also in:
linux-doc, linux-hardening, linux-mm, linux-rt-devel, lkml
Subsystem:
kernel hardening (not covered by other areas), memory management, the rest · Maintainers:
Kees Cook, Andrew Morton, Linus Torvalds
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