4.9-stable review patch. If anyone has any objections, please let me know.
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From: Sven Eckelmann sven@narfation.org
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: syzbot+c764de0fcfadca9a8595@syzkaller.appspotmail.com Reported-by: Dmitry Vyukov dvyukov@google.com Signed-off-by: Sven Eckelmann sven@narfation.org Signed-off-by: Simon Wunderlich sw@simonwunderlich.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -19,7 +19,6 @@ #include "main.h"
#include <linux/atomic.h> -#include <linux/bug.h> #include <linux/byteorder/generic.h> #include <linux/errno.h> #include <linux/fs.h> @@ -172,8 +171,10 @@ static bool batadv_is_on_batman_iface(co parent_dev = __dev_get_by_index((struct net *)parent_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; + }
if (batadv_mutual_parents(net_dev, net, parent_dev, parent_net)) return false;