The check_heap_object() checks the spanning multiple pages and slab.
When the page-spanning test is disabled, the check_heap_object() is
redundant for spanning multiple pages. However, the kernel stacks are
multiple pages under certain conditions: CONFIG_ARCH_THREAD_STACK_ALLOCATOR
is not defined and (THREAD_SIZE >= PAGE_SIZE). At this point, We can skip
the check_heap_object() for kernel stacks to improve performance.
Similarly, the virtually-mapped stack can skip check_heap_object() also,
beacause virt_addr_valid() will return.
I launched more than 100 apps on smartphone, and recorded total check time
and numbers of kernel stacks. The average time of checking kernel stacks
reduced by 48%.
Signed-off-by: Xiaofeng Yuan <yuanxiaofeng1@xxxxxxxxxx>
---
mm/usercopy.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/mm/usercopy.c b/mm/usercopy.c
index e9e9325..af350f6 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -255,6 +255,29 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user)
/* Check for invalid addresses. */
check_bogus_address((const unsigned long)ptr, n, to_user);
+#if !defined(CONFIG_HARDENED_USERCOPY_PAGESPAN) && \
+ !defined(CONFIG_ARCH_THREAD_STACK_ALLOCATOR) && \
+ (THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK))
+ /* Check for bad stack object. */
+ switch (check_stack_object(ptr, n)) {
+ case NOT_STACK:
+ /* Object is not touching the current process stack. */
+ break;
+ case GOOD_FRAME:
+ case GOOD_STACK:
+ /*
+ * Object is either in the correct frame (when it
+ * is possible to check) or just generally on the
+ * process stack (when frame checking not available).
+ */
+ return;
+ default:
+ usercopy_abort("process stack", NULL, to_user, 0, n);
+ }
+
+ /* Check for bad heap object. */
+ check_heap_object(ptr, n, to_user);
+#else
/* Check for bad heap object. */
check_heap_object(ptr, n, to_user);
@@ -274,6 +297,7 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user)
default:
usercopy_abort("process stack", NULL, to_user, 0, n);
}
+#endif
/* Check for object in kernel to avoid text exposure. */
check_kernel_text_object((const unsigned long)ptr, n, to_user);
--
1.9.1
