cris: buggered copy_from_user/copy_to_user/clear_user

commit eb47e029 upstream.

* copy_from_user() on access_ok() failure ought to zero the destination
* none of those primitives should skip the access_ok() check in case of
small constant size.
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/cris/include/asm/uaccess.h

@@ -176,30 +176,6 @@ extern unsigned long __copy_user(void __user *to, const void *from, unsigned lon
 extern unsigned long __copy_user_zeroing(void *to, const void __user *from, unsigned long n);
 extern unsigned long __do_clear_user(void __user *to, unsigned long n);
 
-static inline unsigned long
-__generic_copy_to_user(void __user *to, const void *from, unsigned long n)
-{
-	if (access_ok(VERIFY_WRITE, to, n))
-		return __copy_user(to,from,n);
-	return n;
-}
-
-static inline unsigned long
-__generic_copy_from_user(void *to, const void __user *from, unsigned long n)
-{
-	if (access_ok(VERIFY_READ, from, n))
-		return __copy_user_zeroing(to,from,n);
-	return n;
-}
-
-static inline unsigned long
-__generic_clear_user(void __user *to, unsigned long n)
-{
-	if (access_ok(VERIFY_WRITE, to, n))
-		return __do_clear_user(to,n);
-	return n;
-}
-
 static inline long
 __strncpy_from_user(char *dst, const char __user *src, long count)
 {
@@ -262,7 +238,7 @@ __constant_copy_from_user(void *to, const void __user *from, unsigned long n)
 	else if (n == 24)
 		__asm_copy_from_user_24(to, from, ret);
 	else
-		ret = __generic_copy_from_user(to, from, n);
+		ret = __copy_user_zeroing(to, from, n);
 
 	return ret;
 }
@@ -312,7 +288,7 @@ __constant_copy_to_user(void __user *to, const void *from, unsigned long n)
 	else if (n == 24)
 		__asm_copy_to_user_24(to, from, ret);
 	else
-		ret = __generic_copy_to_user(to, from, n);
+		ret = __copy_user(to, from, n);
 
 	return ret;
 }
@@ -344,26 +320,43 @@ __constant_clear_user(void __user *to, unsigned long n)
 	else if (n == 24)
 		__asm_clear_24(to, ret);
 	else
-		ret = __generic_clear_user(to, n);
+		ret = __do_clear_user(to, n);
 
 	return ret;
 }
 
 
-#define clear_user(to, n)			\
-(__builtin_constant_p(n) ?			\
- __constant_clear_user(to, n) :			\
- __generic_clear_user(to, n))
+static inline size_t clear_user(void __user *to, size_t n)
+{
+	if (unlikely(!access_ok(VERIFY_WRITE, to, n)))
+		return n;
+	if (__builtin_constant_p(n))
+		return __constant_clear_user(to, n);
+	else
+		return __do_clear_user(to, n);
+}
 
-#define copy_from_user(to, from, n)		\
-(__builtin_constant_p(n) ?			\
- __constant_copy_from_user(to, from, n) :	\
- __generic_copy_from_user(to, from, n))
+static inline size_t copy_from_user(void *to, const void __user *from, size_t n)
+{
+	if (unlikely(!access_ok(VERIFY_READ, from, n))) {
+		memset(to, 0, n);
+		return n;
+	}
+	if (__builtin_constant_p(n))
+		return __constant_copy_from_user(to, from, n);
+	else
+		return __copy_user_zeroing(to, from, n);
+}
 
-#define copy_to_user(to, from, n)		\
-(__builtin_constant_p(n) ?			\
- __constant_copy_to_user(to, from, n) :		\
- __generic_copy_to_user(to, from, n))
+static inline size_t copy_to_user(void __user *to, const void *from, size_t n)
+{
+	if (unlikely(!access_ok(VERIFY_WRITE, to, n)))
+		return n;
+	if (__builtin_constant_p(n))
+		return __constant_copy_to_user(to, from, n);
+	else
+		return __copy_user(to, from, n);
+}
 
 /* We let the __ versions of copy_from/to_user inline, because they're often
  * used in fast paths and have only a small space overhead.