[PATCH] llc2: Fix return statement of llc_stat_ev_rx_null_dsap_xid_c (and _test_c)

[PATCH] llc2: Fix return statement of llc_stat_ev_rx_null_dsap_xid_c (and _test_c)

[Chan Shu Tak, Alex]

From: "Chan Shu Tak, Alex" <alexchan@task.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 return statement of llc_stat_ev_rx_null_dsap_xid_c returns 1
when the incoming frame is not a NULL XID frame and 0 otherwise. Hence, a
NULL XID response is returned unexpectedly, e.g. when the incoming frame is
a NULL TEST command.

To fix the error, simply remove the conditional operator.

A similar error in llc_stat_ev_rx_null_dsap_test_c is also fixed.

Signed-off-by: Chan Shu Tak, Alex <alexchan@task.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 204a835..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 ? 0 : 1;			/* 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 ? 0 : 1;			/* NULL DSAP */
+	       !pdu->dsap;				/* NULL DSAP */
 }
 
 static int llc_station_ac_send_xid_r(struct sk_buff *skb)
-- 
1.8.3.1

Re: [PATCH] llc2: Fix return statement of llc_stat_ev_rx_null_dsap_xid_c (and _test_c)

[David Miller]

From: "Chan Shu Tak, Alex" <alexchan@task.com.hk>
Date: Thu, 19 Dec 2019 14:16:18 +0800

> From: "Chan Shu Tak, Alex" <alexchan@task.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 return statement of llc_stat_ev_rx_null_dsap_xid_c returns 1
> when the incoming frame is not a NULL XID frame and 0 otherwise. Hence, a
> NULL XID response is returned unexpectedly, e.g. when the incoming frame is
> a NULL TEST command.
> 
> To fix the error, simply remove the conditional operator.
> 
> A similar error in llc_stat_ev_rx_null_dsap_test_c is also fixed.
> 
> Signed-off-by: Chan Shu Tak, Alex <alexchan@task.com.hk>

Applied.