batman-adv: Avoid WARN_ON timing related checks

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@i-love.sakura.ne.jp>
Reported-by: syzbot+c0b807de416427ff3dd1@syzkaller.appspotmail.com
Fixes: ef0a937f7a14 ("batman-adv: consider outgoing interface in OGM sending")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
[ bp: 4.4 backported: adjust context. ]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c
index caea5bb38d4b066d12667e00f5c91b5d3f4d698b..6f8d2fe114f65ae5db1880ca9b925d7b99e6120b 100644 (file)
--- 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 batadv_forw_packet *forw_packet)
        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;