BACKPORT: usercopy: fold builtin_const check into inline function

Instead of having each caller of check_object_size() need to remember to
check for a const size parameter, move the check into check_object_size()
itself. This actually matches the original implementation in PaX, though
this commit cleans up the now-redundant builtin_const() calls in the
various architectures.

Signed-off-by: Kees Cook <keescook@chromium.org>
Change-Id: I348809399c10ffa051251866063be674d064b9ff
(cherry picked from 81409e9e28058811c9ea865345e1753f8f677e44)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 0ae29ff9ccfde0dfbbcee5ee9c19032064fb45aa..eded095fe81e5c3ddc04e2af91f5bdaf9e4d28a5 100644 (file)
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -161,7 +161,8 @@ extern void __check_object_size(const void *ptr, unsigned long n,
 static inline void check_object_size(const void *ptr, unsigned long n,
                                     bool to_user)
 {
-       __check_object_size(ptr, n, to_user);
+       if (!__builtin_constant_p(n))
+               __check_object_size(ptr, n, to_user);
 }
 #else
 static inline void check_object_size(const void *ptr, unsigned long n,