kmsg: /dev/kmsg - properly return possible copy_from_user() failure

Reported-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NKay Sievers <kay@vrfy.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/printk.c

@@ -389,8 +389,10 @@ static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
 
 	line = buf;
 	for (i = 0; i < count; i++) {
-		if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
+		if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
+			ret = -EFAULT;
 			goto out;
+		}
 		line += iv[i].iov_len;
 	}