From b2dc32dcba08bf55cec600caa76f4afd2e3614df Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Tue, 27 Jun 2023 14:38:12 +0200 Subject: net/sched: act_ipt: add sanity checks on skb before calling target Netfilter targets make assumptions on the skb state, for example iphdr is supposed to be in the linear area. This is normally done by IP stack, but in act_ipt case no such checks are made. Some targets can even assume that skb_dst will be valid. Make a minimum effort to check for this: - Don't call the targets eval function for non-ipv4 skbs. - Don't call the targets eval function for POSTROUTING emulation when the skb has no dst set. v3: use skb_protocol helper (Davide Caratti) Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Florian Westphal Reviewed-by: Simon Horman Acked-by: Jamal Hadi Salim Signed-off-by: Paolo Abeni --- net/sched/act_ipt.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'net/sched') diff --git a/net/sched/act_ipt.c b/net/sched/act_ipt.c index ea7f151e7dd2..a6b522b512dc 100644 --- a/net/sched/act_ipt.c +++ b/net/sched/act_ipt.c @@ -230,6 +230,26 @@ static int tcf_xt_init(struct net *net, struct nlattr *nla, a, &act_xt_ops, tp, flags); } +static bool tcf_ipt_act_check(struct sk_buff *skb) +{ + const struct iphdr *iph; + unsigned int nhoff, len; + + if (!pskb_may_pull(skb, sizeof(struct iphdr))) + return false; + + nhoff = skb_network_offset(skb); + iph = ip_hdr(skb); + if (iph->ihl < 5 || iph->version != 4) + return false; + + len = skb_ip_totlen(skb); + if (skb->len < nhoff + len || len < (iph->ihl * 4u)) + return false; + + return pskb_may_pull(skb, iph->ihl * 4u); +} + TC_INDIRECT_SCOPE int tcf_ipt_act(struct sk_buff *skb, const struct tc_action *a, struct tcf_result *res) @@ -244,9 +264,22 @@ TC_INDIRECT_SCOPE int tcf_ipt_act(struct sk_buff *skb, .pf = NFPROTO_IPV4, }; + if (skb_protocol(skb, false) != htons(ETH_P_IP)) + return TC_ACT_UNSPEC; + if (skb_unclone(skb, GFP_ATOMIC)) return TC_ACT_UNSPEC; + if (!tcf_ipt_act_check(skb)) + return TC_ACT_UNSPEC; + + if (state.hook == NF_INET_POST_ROUTING) { + if (!skb_dst(skb)) + return TC_ACT_UNSPEC; + + state.out = skb->dev; + } + spin_lock(&ipt->tcf_lock); tcf_lastuse_update(&ipt->tcf_tm); -- cgit v1.2.3