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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Marc Kleine-Budde" <mkl@pengutronix.de>,
        syzbot+e3b775f40babeff6e68b@syzkaller.appspotmail.com,
        "Dmitry Vyukov" <dvyukov@google.com>,
        "Oliver Hartkopp" <socketcan@hartkopp.net>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
Message-ID: <lsq.1519831218.206733726@decadent.org.uk>
Subject: [PATCH 3.16 220/254] can: af_can: canfd_rcv(): replace WARN_ONCE
 by pr_warn_once
In-Reply-To: <lsq.1519831217.271785318@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Kleine-Budde <mkl@pengutronix.de>

commit d4689846881d160a4d12a514e991a740bcb5d65a upstream.

If an invalid CANFD frame is received, from a driver or from a tun
interface, a Kernel warning is generated.

This patch replaces the WARN_ONCE by a simple pr_warn_once, so that a
kernel, bootet with panic_on_warn, does not panic. A printk seems to be
more appropriate here.

Reported-by: syzbot+e3b775f40babeff6e68b@syzkaller.appspotmail.com
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
[bwh: Backported to 3.16:
 - Keep using the 'drop' label, as it has another user
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -742,13 +742,12 @@ static int canfd_rcv(struct sk_buff *skb
 	if (unlikely(!net_eq(dev_net(dev), &init_net)))
 		goto drop;
 
-	if (WARN_ONCE(dev->type != ARPHRD_CAN ||
-		      skb->len != CANFD_MTU ||
-		      cfd->len > CANFD_MAX_DLEN,
-		      "PF_CAN: dropped non conform CAN FD skbuf: "
-		      "dev type %d, len %d, datalen %d\n",
-		      dev->type, skb->len, cfd->len))
+	if (unlikely(dev->type != ARPHRD_CAN || skb->len != CANFD_MTU ||
+		     cfd->len > CANFD_MAX_DLEN)) {
+		pr_warn_once("PF_CAN: dropped non conform CAN FD skbuf: dev type %d, len %d, datalen %d\n",
+			     dev->type, skb->len, cfd->len);
 		goto drop;
+	}
 
 	can_receive(skb, dev);
 	return NET_RX_SUCCESS;