linux-kernel - [PATCH net v2 3/3] can: j1939: j1939_tp_cmd_recv(): check the dst address of TP.CM

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Date:   Thu, 28 Oct 2021 22:38:27 +0800
From:   Zhang Changzhong <zhangchangzhong@...wei.com>
To:     Robin van der Gracht <robin@...tonic.nl>,
        Oleksij Rempel <linux@...pel-privat.de>,
        <kernel@...gutronix.de>, Oliver Hartkopp <socketcan@...tkopp.net>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     Zhang Changzhong <zhangchangzhong@...wei.com>,
        <linux-can@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH net v2 3/3] can: j1939: j1939_tp_cmd_recv(): check the dst address of TP.CM_BAM

The TP.CM_BAM message must be sent to the global address [1], so add a
check to drop TP.CM_BAM sent to a non-global address.

Without this patch, the receiver will treat the following packets as
normal RTS/CTS tranport:
18EC0102#20090002FF002301
18EB0102#0100000000000000
18EB0102#020000FFFFFFFFFF

[1] SAE-J1939-82 2015 A.3.3 Row 1.

Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Zhang Changzhong <zhangchangzhong@...wei.com>
---
 net/can/j1939/transport.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 05eb3d0..a271688 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -2023,6 +2023,11 @@ static void j1939_tp_cmd_recv(struct j1939_priv *priv, struct sk_buff *skb)
 		extd = J1939_ETP;
 		fallthrough;
 	case J1939_TP_CMD_BAM:
+		if (cmd == J1939_TP_CMD_BAM && !j1939_cb_is_broadcast(skcb)) {
+			netdev_err_once(priv->ndev, "%s: BAM to unicast (%02x), ignoring!\n",
+					__func__, skcb->addr.sa);
+			return;
+		}
 		fallthrough;
 	case J1939_TP_CMD_RTS:
 		if (skcb->addr.type != extd)
-- 
2.9.5