[PATCH 3.16 283/346] parisc: fix copy_from_user()

[Ben Hutchings]

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

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

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit aace880feea38875fbc919761b77e5732a3659ef upstream.

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/parisc/include/asm/uaccess.h
+++ b/arch/parisc/include/asm/uaccess.h
@@ -9,6 +9,8 @@
 #include <asm/errno.h>
 #include <asm-generic/uaccess-unaligned.h>
 
+#include <linux/string.h>
+
 #define VERIFY_READ 0
 #define VERIFY_WRITE 1
 
@@ -248,13 +250,14 @@ static inline unsigned long __must_check
                                           unsigned long n)
 {
         int sz = __compiletime_object_size(to);
-        int ret = -EFAULT;
+        unsigned long ret = n;
 
         if (likely(sz == -1 || !__builtin_constant_p(n) || sz >= n))
                 ret = __copy_from_user(to, from, n);
         else
                 copy_from_user_overflow();
-
+	if (unlikely(ret))
+		memset(to + (n - ret), 0, ret);
         return ret;
 }