[PATCH 3.16 276/346] ia64: copy_from_user() should zero the destination on access_ok() failure

[Ben Hutchings]

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit a5e541f796f17228793694d64b507f5f57db4cd7 upstream.

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: no calls to check_object_size()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/ia64/include/asm/uaccess.h
+++ b/arch/ia64/include/asm/uaccess.h
@@ -262,17 +262,15 @@ __copy_from_user (void *to, const void _
 	__cu_len;									\
 })
 
-#define copy_from_user(to, from, n)							\
-({											\
-	void *__cu_to = (to);								\
-	const void __user *__cu_from = (from);						\
-	long __cu_len = (n);								\
-											\
-	__chk_user_ptr(__cu_from);							\
-	if (__access_ok(__cu_from, __cu_len, get_fs()))					\
-		__cu_len = __copy_user((__force void __user *) __cu_to, __cu_from, __cu_len);	\
-	__cu_len;									\
-})
+static inline unsigned long
+copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+	if (likely(__access_ok(from, n, get_fs())))
+		n = __copy_user((__force void __user *) to, from, n);
+	else
+		memset(to, 0, n);
+	return n;
+}
 
 #define __copy_in_user(to, from, size)	__copy_user((to), (from), (size))