TOMOYO: Fix infinite loop bug when reading /sys/kernel/security/tomoyo/audit

In tomoyo_flush(), head->r.w[0] holds pointer to string data to be printed.
But head->r.w[0] was updated only when the string data was partially
printed (because head->r.w[0] will be updated by head->r.w[1] later if
completely printed). However, regarding /sys/kernel/security/tomoyo/query ,
an additional '\0' is printed after the string data was completely printed.
But if free space for read buffer became 0 before printing the additional '\0',
tomoyo_flush() was returning without updating head->r.w[0]. As a result,
tomoyo_flush() forever reprints already printed string data.
Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NJames Morris <jmorris@namei.org>

security/tomoyo/common.c

@@ -108,10 +108,9 @@ static bool tomoyo_flush(struct tomoyo_io_buffer *head)
 			head->read_user_buf += len;
 			w += len;
 		}
-		if (*w) {
-			head->r.w[0] = w;
+		head->r.w[0] = w;
+		if (*w)
 			return false;
-		}
 		/* Add '\0' for query. */
 		if (head->poll) {
 			if (!head->read_user_buf_avail ||