Commit ffd219ef authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: nfnetlink: fix warn in nfnetlink_unbind 



syzbot reports following warn:
WARNING: CPU: 0 PID: 3600 at net/netfilter/nfnetlink.c:703 nfnetlink_unbind+0x357/0x3b0 net/netfilter/nfnetlink.c:694

The syzbot generated program does this:

socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER) = 3
setsockopt(3, SOL_NETLINK, NETLINK_DROP_MEMBERSHIP, [1], 4) = 0

... which triggers 'WARN_ON_ONCE(nfnlnet->ctnetlink_listeners == 0)' check.

Instead of counting, just enable reporting for every bind request
and check if we still have listeners on unbind.

While at it, also add the needed bounds check on nfnl_group2type[]
access.

Reported-by: default avatar <syzbot+4903218f7fba0a2d6226@syzkaller.appspotmail.com>
Reported-by: default avatar <syzbot+afd2d80e495f96049571@syzkaller.appspotmail.com>
Fixes: 2794cdb0 ("netfilter: nfnetlink: allow to detect if ctnetlink listeners exist")
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 02ded5a1

net/netfilter/nfnetlink.c

+5 −19
Original line number Original line Diff line number Diff line
@@ -45,7 +45,6 @@ MODULE_DESCRIPTION("Netfilter messages via netlink socket"); 
static unsigned int nfnetlink_pernet_id __read_mostly;

static unsigned int nfnetlink_pernet_id __read_mostly;





struct nfnl_net {

struct nfnl_net {

	unsigned int ctnetlink_listeners;

	struct sock *nfnl;

	struct sock *nfnl;

};

};
@@ -673,17 +672,7 @@ static int nfnetlink_bind(struct net *net, int group) 




#ifdef CONFIG_NF_CONNTRACK_EVENTS

#ifdef CONFIG_NF_CONNTRACK_EVENTS

	if (type == NFNL_SUBSYS_CTNETLINK) {

	if (type == NFNL_SUBSYS_CTNETLINK) {

		struct nfnl_net *nfnlnet = nfnl_pernet(net);



		nfnl_lock(NFNL_SUBSYS_CTNETLINK);

		nfnl_lock(NFNL_SUBSYS_CTNETLINK);



		if (WARN_ON_ONCE(nfnlnet->ctnetlink_listeners == UINT_MAX)) {

			nfnl_unlock(NFNL_SUBSYS_CTNETLINK);

			return -EOVERFLOW;

		}



		nfnlnet->ctnetlink_listeners++;

		if (nfnlnet->ctnetlink_listeners == 1)

		WRITE_ONCE(net->ct.ctnetlink_has_listener, true);

		WRITE_ONCE(net->ct.ctnetlink_has_listener, true);

		nfnl_unlock(NFNL_SUBSYS_CTNETLINK);

		nfnl_unlock(NFNL_SUBSYS_CTNETLINK);

	}

	}
@@ -694,15 +683,12 @@ static int nfnetlink_bind(struct net *net, int group) 
static void nfnetlink_unbind(struct net *net, int group)

static void nfnetlink_unbind(struct net *net, int group)

{

{

#ifdef CONFIG_NF_CONNTRACK_EVENTS

#ifdef CONFIG_NF_CONNTRACK_EVENTS

	int type = nfnl_group2type[group];

	if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)



		return;

	if (type == NFNL_SUBSYS_CTNETLINK) {

		struct nfnl_net *nfnlnet = nfnl_pernet(net);





	if (nfnl_group2type[group] == NFNL_SUBSYS_CTNETLINK) {

		nfnl_lock(NFNL_SUBSYS_CTNETLINK);

		nfnl_lock(NFNL_SUBSYS_CTNETLINK);

		WARN_ON_ONCE(nfnlnet->ctnetlink_listeners == 0);

		if (!nfnetlink_has_listeners(net, group))

		nfnlnet->ctnetlink_listeners--;

		if (nfnlnet->ctnetlink_listeners == 0)

			WRITE_ONCE(net->ct.ctnetlink_has_listener, false);

			WRITE_ONCE(net->ct.ctnetlink_has_listener, false);

		nfnl_unlock(NFNL_SUBSYS_CTNETLINK);

		nfnl_unlock(NFNL_SUBSYS_CTNETLINK);

	}

	}