From: Sven Eckelmann Date: Mon, 21 Aug 2023 19:48:48 +0000 (+0200) Subject: batman-adv: Hold rtnl lock during MTU update via netlink X-Git-Tag: v6.6.7~2156^2~7 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=987aae75fc1041072941ffb622b45ce2359a99b9;p=platform%2Fkernel%2Flinux-starfive.git batman-adv: Hold rtnl lock during MTU update via netlink 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: syzbot+f8812454d9b3ac00d282@syzkaller.appspotmail.com Fixes: c6a953cce8d0 ("batman-adv: Trigger events for auto adjusted MTU") Signed-off-by: Sven Eckelmann Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20230821-batadv-missing-mtu-rtnl-lock-v1-1-1c5a7bfe861e@narfation.org Signed-off-by: Jakub Kicinski --- diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c index ad5714f..6efbc92 100644 --- a/net/batman-adv/netlink.c +++ b/net/batman-adv/netlink.c @@ -495,7 +495,10 @@ 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]) {