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Commit c5f26182 authored by Sven Eckelmann's avatar Sven Eckelmann Committed by Greg Kroah-Hartman
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batman-adv: Hold rtnl lock during MTU update via netlink 



commit 987aae75fc1041072941ffb622b45ce2359a99b9 upstream.

The automatic recalculation of the maximum allowed MTU is usually triggered
by code sections which are already rtnl lock protected by callers outside
of batman-adv. But when the fragmentation setting is changed via
batman-adv's own batadv genl family, then the rtnl lock is not yet taken.

But dev_set_mtu requires that the caller holds the rtnl lock because it
uses netdevice notifiers. And this code will then fail the check for this
lock:

  RTNL: assertion failed at net/core/dev.c (1953)

Cc: stable@vger.kernel.org
Reported-by: default avatar <syzbot+f8812454d9b3ac00d282@syzkaller.appspotmail.com>
Fixes: c6a953cce8d0 ("batman-adv: Trigger events for auto adjusted MTU")
Signed-off-by: default avatarSven Eckelmann <sven@narfation.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230821-batadv-missing-mtu-rtnl-lock-v1-1-1c5a7bfe861e@narfation.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 61b71562

net/batman-adv/netlink.c

+3 −0
Original line number Diff line number Diff line
@@ -496,7 +496,10 @@ static int batadv_netlink_set_mesh(struct sk_buff *skb, struct genl_info *info) 
		attr = info->attrs[BATADV_ATTR_FRAGMENTATION_ENABLED];



		atomic_set(&bat_priv->fragmentation, !!nla_get_u8(attr));



		rtnl_lock();

		batadv_update_min_mtu(bat_priv->soft_iface);

		rtnl_unlock();

	}



	if (info->attrs[BATADV_ATTR_GW_BANDWIDTH_DOWN]) {