netfilter: ipv4: fix NULL dereference

Commit fa50d974d104 ("ipv4: Namespaceify ip_default_ttl sysctl knob")
use sock_net(skb->sk) to get the net namespace, but we can't assume
that sk_buff->sk is always exist, so when it is NULL, oops will happen.

Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Reviewed-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/bridge/netfilter/nft_reject_bridge.c b/net/bridge/netfilter/nft_reject_bridge.c
index adc8d7221dbbc135fa3506a713c70c1130c51ad6..77f7e7a9ebe1f7377198e26f8b3c499d1506b179 100644 (file)
--- a/net/bridge/netfilter/nft_reject_bridge.c
+++ b/net/bridge/netfilter/nft_reject_bridge.c
@@ -40,7 +40,8 @@ static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb,
 /* We cannot use oldskb->dev, it can be either bridge device (NF_BRIDGE INPUT)
  * or the bridge port (NF_BRIDGE PREROUTING).
  */
-static void nft_reject_br_send_v4_tcp_reset(struct sk_buff *oldskb,
+static void nft_reject_br_send_v4_tcp_reset(struct net *net,
+                                           struct sk_buff *oldskb,
                                            const struct net_device *dev,
                                            int hook)
 {
@@ -48,7 +49,6 @@ static void nft_reject_br_send_v4_tcp_reset(struct sk_buff *oldskb,
        struct iphdr *niph;
        const struct tcphdr *oth;
        struct tcphdr _oth;
-       struct net *net = sock_net(oldskb->sk);
 
        if (!nft_bridge_iphdr_validate(oldskb))
                return;
@@ -75,7 +75,8 @@ static void nft_reject_br_send_v4_tcp_reset(struct sk_buff *oldskb,
        br_deliver(br_port_get_rcu(dev), nskb);
 }
 
-static void nft_reject_br_send_v4_unreach(struct sk_buff *oldskb,
+static void nft_reject_br_send_v4_unreach(struct net *net,
+                                         struct sk_buff *oldskb,
                                          const struct net_device *dev,
                                          int hook, u8 code)
 {
@@ -86,7 +87,6 @@ static void nft_reject_br_send_v4_unreach(struct sk_buff *oldskb,
        void *payload;
        __wsum csum;
        u8 proto;
-       struct net *net = sock_net(oldskb->sk);
 
        if (oldskb->csum_bad || !nft_bridge_iphdr_validate(oldskb))
                return;
@@ -273,17 +273,17 @@ static void nft_reject_bridge_eval(const struct nft_expr *expr,
        case htons(ETH_P_IP):
                switch (priv->type) {
                case NFT_REJECT_ICMP_UNREACH:
-                       nft_reject_br_send_v4_unreach(pkt->skb, pkt->in,
-                                                     pkt->hook,
+                       nft_reject_br_send_v4_unreach(pkt->net, pkt->skb,
+                                                     pkt->in, pkt->hook,
                                                      priv->icmp_code);
                        break;
                case NFT_REJECT_TCP_RST:
-                       nft_reject_br_send_v4_tcp_reset(pkt->skb, pkt->in,
-                                                       pkt->hook);
+                       nft_reject_br_send_v4_tcp_reset(pkt->net, pkt->skb,
+                                                       pkt->in, pkt->hook);
                        break;
                case NFT_REJECT_ICMPX_UNREACH:
-                       nft_reject_br_send_v4_unreach(pkt->skb, pkt->in,
-                                                     pkt->hook,
+                       nft_reject_br_send_v4_unreach(pkt->net, pkt->skb,
+                                                     pkt->in, pkt->hook,
                                                      nft_reject_icmp_code(priv->icmp_code));
                        break;
                }

diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c
index 7b8fbb35287785ff4cf3168c47a2e251969e8254..db5b875094465ca4b5f79435f46080fc5f612569 100644 (file)
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -18,10 +18,10 @@
 #include <net/netfilter/nf_conntrack_synproxy.h>
 
 static struct iphdr *
-synproxy_build_ip(struct sk_buff *skb, __be32 saddr, __be32 daddr)
+synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
+                 __be32 daddr)
 {
        struct iphdr *iph;
-       struct net *net = sock_net(skb->sk);
 
        skb_reset_network_header(skb);
        iph = (struct iphdr *)skb_put(skb, sizeof(*iph));
@@ -40,14 +40,12 @@ synproxy_build_ip(struct sk_buff *skb, __be32 saddr, __be32 daddr)
 }
 
 static void
-synproxy_send_tcp(const struct synproxy_net *snet,
+synproxy_send_tcp(struct net *net,
                  const struct sk_buff *skb, struct sk_buff *nskb,
                  struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
                  struct iphdr *niph, struct tcphdr *nth,
                  unsigned int tcp_hdr_size)
 {
-       struct net *net = nf_ct_net(snet->tmpl);
-
        nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
        nskb->ip_summed   = CHECKSUM_PARTIAL;
        nskb->csum_start  = (unsigned char *)nth - nskb->head;
@@ -72,7 +70,7 @@ free_nskb:
 }
 
 static void
-synproxy_send_client_synack(const struct synproxy_net *snet,
+synproxy_send_client_synack(struct net *net,
                            const struct sk_buff *skb, const struct tcphdr *th,
                            const struct synproxy_options *opts)
 {
@@ -91,7 +89,7 @@ synproxy_send_client_synack(const struct synproxy_net *snet,
                return;
        skb_reserve(nskb, MAX_TCP_HEADER);
 
-       niph = synproxy_build_ip(nskb, iph->daddr, iph->saddr);
+       niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 
        skb_reset_transport_header(nskb);
        nth = (struct tcphdr *)skb_put(nskb, tcp_hdr_size);
@@ -109,15 +107,16 @@ synproxy_send_client_synack(const struct synproxy_net *snet,
 
        synproxy_build_options(nth, opts);
 
-       synproxy_send_tcp(snet, skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
+       synproxy_send_tcp(net, skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
                          niph, nth, tcp_hdr_size);
 }
 
 static void
-synproxy_send_server_syn(const struct synproxy_net *snet,
+synproxy_send_server_syn(struct net *net,
                         const struct sk_buff *skb, const struct tcphdr *th,
                         const struct synproxy_options *opts, u32 recv_seq)
 {
+       struct synproxy_net *snet = synproxy_pernet(net);
        struct sk_buff *nskb;
        struct iphdr *iph, *niph;
        struct tcphdr *nth;
@@ -132,7 +131,7 @@ synproxy_send_server_syn(const struct synproxy_net *snet,
                return;
        skb_reserve(nskb, MAX_TCP_HEADER);
 
-       niph = synproxy_build_ip(nskb, iph->saddr, iph->daddr);
+       niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
 
        skb_reset_transport_header(nskb);
        nth = (struct tcphdr *)skb_put(nskb, tcp_hdr_size);
@@ -153,12 +152,12 @@ synproxy_send_server_syn(const struct synproxy_net *snet,
 
        synproxy_build_options(nth, opts);
 
-       synproxy_send_tcp(snet, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
+       synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
                          niph, nth, tcp_hdr_size);
 }
 
 static void
-synproxy_send_server_ack(const struct synproxy_net *snet,
+synproxy_send_server_ack(struct net *net,
                         const struct ip_ct_tcp *state,
                         const struct sk_buff *skb, const struct tcphdr *th,
                         const struct synproxy_options *opts)
@@ -177,7 +176,7 @@ synproxy_send_server_ack(const struct synproxy_net *snet,
                return;
        skb_reserve(nskb, MAX_TCP_HEADER);
 
-       niph = synproxy_build_ip(nskb, iph->daddr, iph->saddr);
+       niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 
        skb_reset_transport_header(nskb);
        nth = (struct tcphdr *)skb_put(nskb, tcp_hdr_size);
@@ -193,11 +192,11 @@ synproxy_send_server_ack(const struct synproxy_net *snet,
 
        synproxy_build_options(nth, opts);
 
-       synproxy_send_tcp(snet, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
+       synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
 }
 
 static void
-synproxy_send_client_ack(const struct synproxy_net *snet,
+synproxy_send_client_ack(struct net *net,
                         const struct sk_buff *skb, const struct tcphdr *th,
                         const struct synproxy_options *opts)
 {
@@ -215,7 +214,7 @@ synproxy_send_client_ack(const struct synproxy_net *snet,
                return;
        skb_reserve(nskb, MAX_TCP_HEADER);
 
-       niph = synproxy_build_ip(nskb, iph->saddr, iph->daddr);
+       niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
 
        skb_reset_transport_header(nskb);
        nth = (struct tcphdr *)skb_put(nskb, tcp_hdr_size);
@@ -231,15 +230,16 @@ synproxy_send_client_ack(const struct synproxy_net *snet,
 
        synproxy_build_options(nth, opts);
 
-       synproxy_send_tcp(snet, skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
+       synproxy_send_tcp(net, skb, nskb, skb->nfct, IP_CT_ESTABLISHED_REPLY,
                          niph, nth, tcp_hdr_size);
 }
 
 static bool
-synproxy_recv_client_ack(const struct synproxy_net *snet,
+synproxy_recv_client_ack(struct net *net,
                         const struct sk_buff *skb, const struct tcphdr *th,
                         struct synproxy_options *opts, u32 recv_seq)
 {
+       struct synproxy_net *snet = synproxy_pernet(net);
        int mss;
 
        mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
@@ -255,7 +255,7 @@ synproxy_recv_client_ack(const struct synproxy_net *snet,
        if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP)
                synproxy_check_timestamp_cookie(opts);
 
-       synproxy_send_server_syn(snet, skb, th, opts, recv_seq);
+       synproxy_send_server_syn(net, skb, th, opts, recv_seq);
        return true;
 }
 
@@ -263,7 +263,8 @@ static unsigned int
 synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
        const struct xt_synproxy_info *info = par->targinfo;
-       struct synproxy_net *snet = synproxy_pernet(par->net);
+       struct net *net = par->net;
+       struct synproxy_net *snet = synproxy_pernet(net);
        struct synproxy_options opts = {};
        struct tcphdr *th, _th;
 
@@ -292,12 +293,12 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
                                          XT_SYNPROXY_OPT_SACK_PERM |
                                          XT_SYNPROXY_OPT_ECN);
 
-               synproxy_send_client_synack(snet, skb, th, &opts);
+               synproxy_send_client_synack(net, skb, th, &opts);
                return NF_DROP;
 
        } else if (th->ack && !(th->fin || th->rst || th->syn)) {
                /* ACK from client */
-               synproxy_recv_client_ack(snet, skb, th, &opts, ntohl(th->seq));
+               synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq));
                return NF_DROP;
        }
 
@@ -308,7 +309,8 @@ static unsigned int ipv4_synproxy_hook(void *priv,
                                       struct sk_buff *skb,
                                       const struct nf_hook_state *nhs)
 {
-       struct synproxy_net *snet = synproxy_pernet(nhs->net);
+       struct net *net = nhs->net;
+       struct synproxy_net *snet = synproxy_pernet(net);
        enum ip_conntrack_info ctinfo;
        struct nf_conn *ct;
        struct nf_conn_synproxy *synproxy;
@@ -365,7 +367,7 @@ static unsigned int ipv4_synproxy_hook(void *priv,
                         * therefore we need to add 1 to make the SYN sequence
                         * number match the one of first SYN.
                         */
-                       if (synproxy_recv_client_ack(snet, skb, th, &opts,
+                       if (synproxy_recv_client_ack(net, skb, th, &opts,
                                                     ntohl(th->seq) + 1))
                                this_cpu_inc(snet->stats->cookie_retrans);
 
@@ -391,12 +393,12 @@ static unsigned int ipv4_synproxy_hook(void *priv,
                                  XT_SYNPROXY_OPT_SACK_PERM);
 
                swap(opts.tsval, opts.tsecr);
-               synproxy_send_server_ack(snet, state, skb, th, &opts);
+               synproxy_send_server_ack(net, state, skb, th, &opts);
 
                nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
 
                swap(opts.tsval, opts.tsecr);
-               synproxy_send_client_ack(snet, skb, th, &opts);
+               synproxy_send_client_ack(net, skb, th, &opts);
 
                consume_skb(skb);
                return NF_STOLEN;