linux-kernel - [PATCH 3.16 219/254] can: af_can: can_rcv(): replace WARN_ONCE by pr_warn

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Message-ID: <lsq.1519831218.196344564@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Dmitry Vyukov" <dvyukov@...gle.com>,
        "Oliver Hartkopp" <socketcan@...tkopp.net>,
        "Marc Kleine-Budde" <mkl@...gutronix.de>,
        syzbot+4386709c0c1284dca827@...kaller.appspotmail.com
Subject: [PATCH 3.16 219/254] can: af_can: can_rcv(): replace WARN_ONCE by
 pr_warn_once

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit 8cb68751c115d176ec851ca56ecfbb411568c9e8 upstream.

If an invalid CAN 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+4386709c0c1284dca827@...kaller.appspotmail.com
Suggested-by: Dmitry Vyukov <dvyukov@...gle.com>
Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
[bwh: Backported to 3.16:
 - Keep using the 'drop' label, as it has another user
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -719,13 +719,12 @@ static int can_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 != CAN_MTU ||
-		      cfd->len > CAN_MAX_DLEN,
-		      "PF_CAN: dropped non conform CAN skbuf: "
-		      "dev type %d, len %d, datalen %d\n",
-		      dev->type, skb->len, cfd->len))
+	if (unlikely(dev->type != ARPHRD_CAN || skb->len != CAN_MTU ||
+		     cfd->len > CAN_MAX_DLEN)) {
+		pr_warn_once("PF_CAN: dropped non conform CAN 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;