diff options
| author | Liping Zhang <zlpnobody@gmail.com> | 2017-05-07 22:01:56 +0800 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2017-05-15 12:42:29 +0200 |
| commit | 9338d7b4418e9996a7642867d8f6b482a6040ed6 (patch) | |
| tree | 5bf37ab11070434ed04c1bcfe12194925bfffd25 /net/netfilter/nfnetlink_cthelper.c | |
| parent | d91fc59cd77c719f33eda65c194ad8f95a055190 (diff) | |
netfilter: nfnl_cthelper: reject del request if helper obj is in use
We can still delete the ct helper even if it is in use, this will cause
a use-after-free error. In more detail, I mean:
# nfct helper add ssdp inet udp
# iptables -t raw -A OUTPUT -p udp -j CT --helper ssdp
# nfct helper delete ssdp //--> oops, succeed!
BUG: unable to handle kernel paging request at 000026ca
IP: 0x26ca
[...]
Call Trace:
? ipv4_helper+0x62/0x80 [nf_conntrack_ipv4]
nf_hook_slow+0x21/0xb0
ip_output+0xe9/0x100
? ip_fragment.constprop.54+0xc0/0xc0
ip_local_out+0x33/0x40
ip_send_skb+0x16/0x80
udp_send_skb+0x84/0x240
udp_sendmsg+0x35d/0xa50
So add reference count to fix this issue, if ct helper is used by
others, reject the delete request.
Apply this patch:
# nfct helper delete ssdp
nfct v1.4.3: netlink error: Device or resource busy
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net/netfilter/nfnetlink_cthelper.c')
| -rw-r--r-- | net/netfilter/nfnetlink_cthelper.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/net/netfilter/nfnetlink_cthelper.c b/net/netfilter/nfnetlink_cthelper.c index 950bf6eadc65..be678a323598 100644 --- a/net/netfilter/nfnetlink_cthelper.c +++ b/net/netfilter/nfnetlink_cthelper.c @@ -686,6 +686,7 @@ static int nfnl_cthelper_del(struct net *net, struct sock *nfnl, tuple_set = true; } + ret = -ENOENT; list_for_each_entry_safe(nlcth, n, &nfnl_cthelper_list, list) { cur = &nlcth->helper; j++; @@ -699,16 +700,20 @@ static int nfnl_cthelper_del(struct net *net, struct sock *nfnl, tuple.dst.protonum != cur->tuple.dst.protonum)) continue; - found = true; - nf_conntrack_helper_unregister(cur); - kfree(cur->expect_policy); + if (refcount_dec_if_one(&cur->refcnt)) { + found = true; + nf_conntrack_helper_unregister(cur); + kfree(cur->expect_policy); - list_del(&nlcth->list); - kfree(nlcth); + list_del(&nlcth->list); + kfree(nlcth); + } else { + ret = -EBUSY; + } } /* Make sure we return success if we flush and there is no helpers */ - return (found || j == 0) ? 0 : -ENOENT; + return (found || j == 0) ? 0 : ret; } static const struct nla_policy nfnl_cthelper_policy[NFCTH_MAX+1] = { |