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netfilter: nfnetlink: fix warn in nfnetlink_unbind

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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: <syzbot+4903218f7fba0a2d6226@syzkaller.appspotmail.com>
Reported-by: <syzbot+afd2d80e495f96049571@syzkaller.appspotmail.com>
Fixes: 2794cdb0b9 ("netfilter: nfnetlink: allow to detect if ctnetlink listeners exist")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2022-05-20 00:02:03 +02:00 committed by Pablo Neira Ayuso
parent 02ded5a173
commit ffd219efd9
1 changed files with 5 additions and 19 deletions
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24
net/netfilter/nfnetlink.c
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@ -45,7 +45,6 @@ MODULE_DESCRIPTION("Netfilter messages via netlink socket");
static unsigned int nfnetlink_pernet_id __read_mostly;
struct nfnl_net {
unsigned int ctnetlink_listeners;
struct sock *nfnl;
};
@ -673,18 +672,8 @@ static int nfnetlink_bind(struct net *net, int group)
#ifdef CONFIG_NF_CONNTRACK_EVENTS
if (type == NFNL_SUBSYS_CTNETLINK) {
struct nfnl_net *nfnlnet = nfnl_pernet(net);
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);
}
#endif
@ -694,15 +683,12 @@ static int nfnetlink_bind(struct net *net, int group)
static void nfnetlink_unbind(struct net *net, int group)
{
#ifdef CONFIG_NF_CONNTRACK_EVENTS
int type = nfnl_group2type[group];
if (type == NFNL_SUBSYS_CTNETLINK) {
struct nfnl_net *nfnlnet = nfnl_pernet(net);
if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
return;
if (nfnl_group2type[group] == NFNL_SUBSYS_CTNETLINK) {
nfnl_lock(NFNL_SUBSYS_CTNETLINK);
WARN_ON_ONCE(nfnlnet->ctnetlink_listeners == 0);
nfnlnet->ctnetlink_listeners--;
if (nfnlnet->ctnetlink_listeners == 0)
if (!nfnetlink_has_listeners(net, group))
WRITE_ONCE(net->ct.ctnetlink_has_listener, false);
nfnl_unlock(NFNL_SUBSYS_CTNETLINK);
}