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Date:   Mon, 18 Feb 2019 14:44:04 +0100
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,,,
        Dmitry Vyukov <>,
        Sven Eckelmann <>,
        Simon Wunderlich <>
Subject: [PATCH 4.4 116/143] batman-adv: Avoid WARN on net_device without parent in netns

4.4-stable review patch.  If anyone has any objections, please let me know.


From: Sven Eckelmann <>

commit 955d3411a17f590364238bd0d3329b61f20c1cd2 upstream.

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: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Reported-by: Dmitry Vyukov <>
Signed-off-by: Sven Eckelmann <>
Signed-off-by: Simon Wunderlich <>
Signed-off-by: Greg Kroah-Hartman <>

 net/batman-adv/hard-interface.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -18,7 +18,6 @@
 #include "hard-interface.h"
 #include "main.h"
-#include <linux/bug.h>
 #include <linux/byteorder/generic.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
@@ -104,8 +103,10 @@ static bool batadv_is_on_batman_iface(co
 	/* recurse over the parent device */
 	parent_dev = __dev_get_by_index(&init_net, dev_get_iflink(net_dev));
 	/* 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;
+	}
 	ret = batadv_is_on_batman_iface(parent_dev);

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