linux-kernel - [PATCH 4.4 159/162] batman-adv: Avoid WARN

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Message-Id: <20211124115703.419182207@linuxfoundation.org>
Date:   Wed, 24 Nov 2021 12:57:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        syzbot+c0b807de416427ff3dd1@...kaller.appspotmail.com,
        Sven Eckelmann <sven@...fation.org>,
        Simon Wunderlich <sw@...onwunderlich.de>
Subject: [PATCH 4.4 159/162] batman-adv: Avoid WARN_ON timing related checks

From: Sven Eckelmann <sven@...fation.org>

commit 9f460ae31c4435fd022c443a6029352217a16ac1 upstream.

The soft/batadv interface for a queued OGM can be changed during the time
the OGM was queued for transmission and when the OGM is actually
transmitted by the worker.

But WARN_ON must be used to denote kernel bugs and not to print simple
warnings. A warning can simply be printed using pr_warn.

Reported-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Reported-by: syzbot+c0b807de416427ff3dd1@...kaller.appspotmail.com
Fixes: ef0a937f7a14 ("batman-adv: consider outgoing interface in OGM sending")
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
[ bp: 4.4 backported: adjust context. ]
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/batman-adv/bat_iv_ogm.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -526,8 +526,10 @@ static void batadv_iv_ogm_emit(struct ba
 	if (WARN_ON(!forw_packet->if_outgoing))
 		goto out;
 
-	if (WARN_ON(forw_packet->if_outgoing->soft_iface != soft_iface))
+	if (forw_packet->if_outgoing->soft_iface != soft_iface) {
+		pr_warn("%s: soft interface switch for queued OGM\n", __func__);
 		goto out;
+	}
 
 	if (forw_packet->if_incoming->if_status != BATADV_IF_ACTIVE)
 		goto out;