microblaze: fix copy_from_user()

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 6 insertions, 3 deletions

diff --git a/arch/microblaze/include/asm/uaccess.h b/arch/microblaze/include/asm/uaccess.h
index 331b0d35f89c..3a486d3b6f52 100644
--- a/arch/microblaze/include/asm/uaccess.h
+++ b/arch/microblaze/include/asm/uaccess.h
@@ -373,10 +373,13 @@ extern long __user_bad(void);
 static inline long copy_from_user(void *to,
                 const void __user *from, unsigned long n)
 {
+        unsigned long res = n;
         might_fault();
-        if (access_ok(VERIFY_READ, from, n))
-                return __copy_from_user(to, from, n);
-        return n;
+        if (likely(access_ok(VERIFY_READ, from, n)))
+                res = __copy_from_user(to, from, n);
+        if (unlikely(res))
+                memset(to + (n - res), 0, res);
+        return res;
 }
 
 #define __copy_to_user(to, from, n)     \