linux-kernel - [PATCH v2] llc2: Remove the condition operator in llc_stat_ev_rx_null_dsap_xid_c and llc_stat_ev_rx_null_dsap_test

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Date:   Tue, 17 Dec 2019 12:00:36 +0800
From:   "Chan Shu Tak, Alex" <alexchan@...k.com.hk>
To:     unlisted-recipients:; (no To-header on input)
Cc:     "Chan Shu Tak, Alex" <alexchan@...k.com.hk>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] llc2: Remove the condition operator in llc_stat_ev_rx_null_dsap_xid_c and llc_stat_ev_rx_null_dsap_test_c.

From: "Chan Shu Tak, Alex" <alexchan@...k.com.hk>

When a frame with NULL DSAP is received, llc_station_rcv is called.
In turn, llc_stat_ev_rx_null_dsap_xid_c is called to check if it is a NULL
XID frame. The original condition operator returns 1 when the incoming
frame is not a NULL XID frame and 0 otherwise. As a result, an incoming
NULL TEST frame would trigger an XID response instead.

To fix the error, we just need to remove the condition operator.

The same error is found in llc_stat_ev_rx_null_dsap_test_c and fixed.

Signed-off-by: Chan Shu Tak, Alex <alexchan@...k.com.hk>
---
 net/llc/llc_station.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/llc/llc_station.c b/net/llc/llc_station.c
index 90955d7..c29170e 100644
--- a/net/llc/llc_station.c
+++ b/net/llc/llc_station.c
@@ -32,7 +32,7 @@ static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
 	return LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
 	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
 	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
-	       !pdu->dsap ? 1 : 0;			/* NULL DSAP value */
+	       !pdu->dsap;				/* NULL DSAP value */
 }
 
 static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
@@ -42,7 +42,7 @@ static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
 	return LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
 	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
 	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
-	       !pdu->dsap ? 1 : 0;			/* NULL DSAP */
+	       !pdu->dsap;				/* NULL DSAP */
 }
 
 static int llc_station_ac_send_xid_r(struct sk_buff *skb)
-- 
1.8.3.1