[maint] batman-adv: Avoid WARN on net_device without parent in netns

Message ID 20181230114601.3546-1-sven@narfation.org (mailing list archive)
State Accepted, archived
Delegated to: Simon Wunderlich
Series [maint] batman-adv: Avoid WARN on net_device without parent in netns |

Commit Message

Sven Eckelmann Dec. 30, 2018, 11:46 a.m. UTC
  It is not allowed to use WARN* helpers on potential incorrect input from
the user or transient problems because systems configured as panic_on_warn
will reboot due to such a problem.

A NULL return value of __dev_get_by_index can be caused by various problems
which can either be related to the system configuration or problems
(incorrectly returned network namespaces) in other (virtual) net_device
drivers. batman-adv should not cause a (harmful) WARN in this situation and
instead only report it via a simple message.

Fixes: 3d48811b27f5 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Reported-by: syzbot+c764de0fcfadca9a8595@syzkaller.appspotmail.com
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Cc: syzbot <syzbot+c764de0fcfadca9a8595@syzkaller.appspotmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: syzkaller-bugs@googlegroups.com
 net/batman-adv/hard-interface.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)


diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 508f4416..5b7632cf 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -20,7 +20,6 @@ 
 #include "main.h"
 #include <linux/atomic.h>
-#include <linux/bug.h>
 #include <linux/byteorder/generic.h>
 #include <linux/errno.h>
 #include <linux/gfp.h>
@@ -179,8 +178,10 @@  static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
 	parent_dev = __dev_get_by_index((struct net *)parent_net,
 	/* if we got a NULL parent_dev there is something broken.. */
-	if (WARN(!parent_dev, "Cannot find parent device"))
+	if (!parent_dev) {
+		pr_err("Cannot find parent device\n");
 		return false;
+	}
 	if (batadv_mutual_parents(net_dev, net, parent_dev, parent_net))
 		return false;