kfifo: kfifo_copy_{to,from}_user: fix copied bytes calculation

'copied' and 'len' are in bytes, while 'ret' is in elements, so we need to
multiply 'ret' with the size of one element to get the correct result.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/kfifo.c

@@ -215,7 +215,7 @@ static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
 	 * incrementing the fifo->in index counter
 	 */
 	smp_wmb();
-	*copied = len - ret;
+	*copied = len - ret * esize;
 	/* return the number of elements which are not copied */
 	return ret;
 }
@@ -275,7 +275,7 @@ static unsigned long kfifo_copy_to_user(struct __kfifo *fifo, void __user *to,
 	 * incrementing the fifo->out index counter
 	 */
 	smp_wmb();
-	*copied = len - ret;
+	*copied = len - ret * esize;
 	/* return the number of elements which are not copied */
 	return ret;
 }