![Dmytro Linkin](/assets/img/avatar_default.png)
Currently init call of all actions (except ipt) init their 'parm'
structure as a direct pointer to nla data in skb. This leads to race
condition when some of the filter actions were initialized successfully
(and were assigned with idr action index that was written directly
into nla data), but then were deleted and retried (due to following
action module missing or classifier-initiated retry), in which case
action init code tries to insert action to idr with index that was
assigned on previous iteration. During retry the index can be reused
by another action that was inserted concurrently, which causes
unintended action sharing between filters.
To fix described race condition, save action idr index to temporary
stack-allocated variable instead on nla data.
Fixes: 0190c1d452
("net: sched: atomically check-allocate action")
Signed-off-by: Dmytro Linkin <dmitrolin@mellanox.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
360 lines
7.8 KiB
C
360 lines
7.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Stateless NAT actions
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*
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* Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
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*/
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/netfilter.h>
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#include <linux/rtnetlink.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/string.h>
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#include <linux/tc_act/tc_nat.h>
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#include <net/act_api.h>
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#include <net/pkt_cls.h>
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#include <net/icmp.h>
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#include <net/ip.h>
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#include <net/netlink.h>
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#include <net/tc_act/tc_nat.h>
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#include <net/tcp.h>
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#include <net/udp.h>
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static unsigned int nat_net_id;
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static struct tc_action_ops act_nat_ops;
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static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
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[TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
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};
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static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
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struct tc_action **a, int ovr, int bind,
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bool rtnl_held, struct tcf_proto *tp,
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struct netlink_ext_ack *extack)
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{
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struct tc_action_net *tn = net_generic(net, nat_net_id);
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struct nlattr *tb[TCA_NAT_MAX + 1];
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struct tcf_chain *goto_ch = NULL;
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struct tc_nat *parm;
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int ret = 0, err;
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struct tcf_nat *p;
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u32 index;
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if (nla == NULL)
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return -EINVAL;
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err = nla_parse_nested_deprecated(tb, TCA_NAT_MAX, nla, nat_policy,
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NULL);
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if (err < 0)
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return err;
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if (tb[TCA_NAT_PARMS] == NULL)
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return -EINVAL;
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parm = nla_data(tb[TCA_NAT_PARMS]);
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index = parm->index;
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err = tcf_idr_check_alloc(tn, &index, a, bind);
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if (!err) {
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ret = tcf_idr_create(tn, index, est, a,
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&act_nat_ops, bind, false);
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if (ret) {
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tcf_idr_cleanup(tn, index);
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return ret;
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}
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ret = ACT_P_CREATED;
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} else if (err > 0) {
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if (bind)
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return 0;
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if (!ovr) {
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tcf_idr_release(*a, bind);
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return -EEXIST;
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}
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} else {
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return err;
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}
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err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
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if (err < 0)
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goto release_idr;
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p = to_tcf_nat(*a);
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spin_lock_bh(&p->tcf_lock);
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p->old_addr = parm->old_addr;
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p->new_addr = parm->new_addr;
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p->mask = parm->mask;
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p->flags = parm->flags;
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goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
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spin_unlock_bh(&p->tcf_lock);
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if (goto_ch)
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tcf_chain_put_by_act(goto_ch);
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if (ret == ACT_P_CREATED)
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tcf_idr_insert(tn, *a);
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return ret;
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release_idr:
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tcf_idr_release(*a, bind);
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return err;
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}
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static int tcf_nat_act(struct sk_buff *skb, const struct tc_action *a,
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struct tcf_result *res)
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{
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struct tcf_nat *p = to_tcf_nat(a);
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struct iphdr *iph;
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__be32 old_addr;
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__be32 new_addr;
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__be32 mask;
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__be32 addr;
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int egress;
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int action;
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int ihl;
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int noff;
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spin_lock(&p->tcf_lock);
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tcf_lastuse_update(&p->tcf_tm);
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old_addr = p->old_addr;
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new_addr = p->new_addr;
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mask = p->mask;
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egress = p->flags & TCA_NAT_FLAG_EGRESS;
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action = p->tcf_action;
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bstats_update(&p->tcf_bstats, skb);
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spin_unlock(&p->tcf_lock);
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if (unlikely(action == TC_ACT_SHOT))
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goto drop;
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noff = skb_network_offset(skb);
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if (!pskb_may_pull(skb, sizeof(*iph) + noff))
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goto drop;
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iph = ip_hdr(skb);
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if (egress)
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addr = iph->saddr;
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else
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addr = iph->daddr;
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if (!((old_addr ^ addr) & mask)) {
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if (skb_try_make_writable(skb, sizeof(*iph) + noff))
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goto drop;
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new_addr &= mask;
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new_addr |= addr & ~mask;
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/* Rewrite IP header */
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iph = ip_hdr(skb);
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if (egress)
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iph->saddr = new_addr;
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else
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iph->daddr = new_addr;
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csum_replace4(&iph->check, addr, new_addr);
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} else if ((iph->frag_off & htons(IP_OFFSET)) ||
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iph->protocol != IPPROTO_ICMP) {
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goto out;
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}
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ihl = iph->ihl * 4;
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/* It would be nice to share code with stateful NAT. */
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switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
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case IPPROTO_TCP:
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{
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struct tcphdr *tcph;
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if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
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skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
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goto drop;
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tcph = (void *)(skb_network_header(skb) + ihl);
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inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
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true);
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break;
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}
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case IPPROTO_UDP:
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{
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struct udphdr *udph;
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if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
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skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
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goto drop;
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udph = (void *)(skb_network_header(skb) + ihl);
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if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
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inet_proto_csum_replace4(&udph->check, skb, addr,
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new_addr, true);
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if (!udph->check)
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udph->check = CSUM_MANGLED_0;
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}
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break;
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}
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case IPPROTO_ICMP:
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{
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struct icmphdr *icmph;
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if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
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goto drop;
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icmph = (void *)(skb_network_header(skb) + ihl);
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if ((icmph->type != ICMP_DEST_UNREACH) &&
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(icmph->type != ICMP_TIME_EXCEEDED) &&
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(icmph->type != ICMP_PARAMETERPROB))
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break;
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if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
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noff))
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goto drop;
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icmph = (void *)(skb_network_header(skb) + ihl);
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iph = (void *)(icmph + 1);
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if (egress)
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addr = iph->daddr;
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else
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addr = iph->saddr;
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if ((old_addr ^ addr) & mask)
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break;
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if (skb_try_make_writable(skb, ihl + sizeof(*icmph) +
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sizeof(*iph) + noff))
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goto drop;
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icmph = (void *)(skb_network_header(skb) + ihl);
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iph = (void *)(icmph + 1);
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new_addr &= mask;
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new_addr |= addr & ~mask;
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/* XXX Fix up the inner checksums. */
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if (egress)
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iph->daddr = new_addr;
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else
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iph->saddr = new_addr;
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inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
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false);
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break;
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}
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default:
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break;
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}
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out:
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return action;
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drop:
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spin_lock(&p->tcf_lock);
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p->tcf_qstats.drops++;
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spin_unlock(&p->tcf_lock);
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return TC_ACT_SHOT;
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}
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static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
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int bind, int ref)
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{
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unsigned char *b = skb_tail_pointer(skb);
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struct tcf_nat *p = to_tcf_nat(a);
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struct tc_nat opt = {
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.index = p->tcf_index,
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.refcnt = refcount_read(&p->tcf_refcnt) - ref,
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.bindcnt = atomic_read(&p->tcf_bindcnt) - bind,
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};
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struct tcf_t t;
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spin_lock_bh(&p->tcf_lock);
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opt.old_addr = p->old_addr;
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opt.new_addr = p->new_addr;
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opt.mask = p->mask;
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opt.flags = p->flags;
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opt.action = p->tcf_action;
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if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
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goto nla_put_failure;
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tcf_tm_dump(&t, &p->tcf_tm);
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if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
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goto nla_put_failure;
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spin_unlock_bh(&p->tcf_lock);
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return skb->len;
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nla_put_failure:
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spin_unlock_bh(&p->tcf_lock);
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nlmsg_trim(skb, b);
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return -1;
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}
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static int tcf_nat_walker(struct net *net, struct sk_buff *skb,
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struct netlink_callback *cb, int type,
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const struct tc_action_ops *ops,
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struct netlink_ext_ack *extack)
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{
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struct tc_action_net *tn = net_generic(net, nat_net_id);
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return tcf_generic_walker(tn, skb, cb, type, ops, extack);
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}
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static int tcf_nat_search(struct net *net, struct tc_action **a, u32 index)
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{
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struct tc_action_net *tn = net_generic(net, nat_net_id);
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return tcf_idr_search(tn, a, index);
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}
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static struct tc_action_ops act_nat_ops = {
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.kind = "nat",
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.id = TCA_ID_NAT,
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.owner = THIS_MODULE,
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.act = tcf_nat_act,
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.dump = tcf_nat_dump,
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.init = tcf_nat_init,
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.walk = tcf_nat_walker,
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.lookup = tcf_nat_search,
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.size = sizeof(struct tcf_nat),
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};
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static __net_init int nat_init_net(struct net *net)
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{
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struct tc_action_net *tn = net_generic(net, nat_net_id);
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return tc_action_net_init(tn, &act_nat_ops);
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}
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static void __net_exit nat_exit_net(struct list_head *net_list)
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{
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tc_action_net_exit(net_list, nat_net_id);
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}
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static struct pernet_operations nat_net_ops = {
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.init = nat_init_net,
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.exit_batch = nat_exit_net,
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.id = &nat_net_id,
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.size = sizeof(struct tc_action_net),
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};
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MODULE_DESCRIPTION("Stateless NAT actions");
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MODULE_LICENSE("GPL");
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static int __init nat_init_module(void)
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{
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return tcf_register_action(&act_nat_ops, &nat_net_ops);
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}
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static void __exit nat_cleanup_module(void)
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{
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tcf_unregister_action(&act_nat_ops, &nat_net_ops);
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}
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module_init(nat_init_module);
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module_exit(nat_cleanup_module);
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