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netfilter: ipv4: fix NULL dereference
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Commit fa50d97 ("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 <[email protected]>
Reviewed-by: Nikolay Borisov <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>
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@ummakynes
Liping Zhang authored and ummakynes committed Mar 28, 2016
1 parent b301f25 commit 2942119
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Showing 2 changed files with 38 additions and 36 deletions.
20 changes: 10 additions & 10 deletions net/bridge/netfilter/nft_reject_bridge.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,15 +40,15 @@ 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)
{
struct sk_buff *nskb;
struct iphdr *niph;
const struct tcphdr *oth;
struct tcphdr _oth;
struct net *net = sock_net(oldskb->sk);

if (!nft_bridge_iphdr_validate(oldskb))
return;
Expand All @@ -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)
{
Expand All @@ -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;
Expand Down Expand Up @@ -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;
}
Expand Down
54 changes: 28 additions & 26 deletions net/ipv4/netfilter/ipt_SYNPROXY.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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));
Expand All @@ -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;
Expand All @@ -72,7 +70,7 @@ synproxy_send_tcp(const struct synproxy_net *snet,
}

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)
{
Expand All @@ -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);
Expand All @@ -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;
Expand All @@ -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);
Expand All @@ -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)
Expand All @@ -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);
Expand All @@ -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)
{
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -255,15 +255,16 @@ 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;
}

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;

Expand Down Expand Up @@ -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;
}

Expand All @@ -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;
Expand Down Expand Up @@ -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);

Expand All @@ -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;
Expand Down

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