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Subject[PATCH 3.18 08/19] tcp: fix more NULL deref after prequeue changes
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 0f85feae6b710ced3abad5b2b47d31dfcb956b62 ]

When I cooked commit c3658e8d0f1 ("tcp: fix possible NULL dereference in
tcp_vX_send_reset()") I missed other spots we could deref a NULL
skb_dst(skb)

Again, if a socket is provided, we do not need skb_dst() to get a
pointer to network namespace : sock_net(sk) is good enough.

Reported-by: Dann Frazier <dann.frazier@canonical.com>
Bisected-by: Dann Frazier <dann.frazier@canonical.com>
Tested-by: Dann Frazier <dann.frazier@canonical.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: ca777eff51f7 ("tcp: remove dst refcount false sharing for prequeue mode")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_ipv4.c | 4 ++--
net/ipv6/tcp_ipv6.c | 28 ++++++++++++++--------------
2 files changed, 16 insertions(+), 16 deletions(-)

--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -623,6 +623,7 @@ static void tcp_v4_send_reset(struct soc
arg.iov[0].iov_base = (unsigned char *)&rep;
arg.iov[0].iov_len = sizeof(rep.th);

+ net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
#ifdef CONFIG_TCP_MD5SIG
hash_location = tcp_parse_md5sig_option(th);
if (!sk && hash_location) {
@@ -633,7 +634,7 @@ static void tcp_v4_send_reset(struct soc
* Incoming packet is checked with md5 hash with finding key,
* no RST generated if md5 hash doesn't match.
*/
- sk1 = __inet_lookup_listener(dev_net(skb_dst(skb)->dev),
+ sk1 = __inet_lookup_listener(net,
&tcp_hashinfo, ip_hdr(skb)->saddr,
th->source, ip_hdr(skb)->daddr,
ntohs(th->source), inet_iif(skb));
@@ -681,7 +682,6 @@ static void tcp_v4_send_reset(struct soc
if (sk)
arg.bound_dev_if = sk->sk_bound_dev_if;

- net = dev_net(skb_dst(skb)->dev);
arg.tos = ip_hdr(skb)->tos;
ip_send_unicast_reply(net, skb, &TCP_SKB_CB(skb)->header.h4.opt,
ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -787,16 +787,16 @@ static const struct tcp_request_sock_ops
.queue_hash_add = inet6_csk_reqsk_queue_hash_add,
};

-static void tcp_v6_send_response(struct sk_buff *skb, u32 seq, u32 ack, u32 win,
- u32 tsval, u32 tsecr, int oif,
- struct tcp_md5sig_key *key, int rst, u8 tclass,
- u32 label)
+static void tcp_v6_send_response(struct sock *sk, struct sk_buff *skb, u32 seq,
+ u32 ack, u32 win, u32 tsval, u32 tsecr,
+ int oif, struct tcp_md5sig_key *key, int rst,
+ u8 tclass, u32 label)
{
const struct tcphdr *th = tcp_hdr(skb);
struct tcphdr *t1;
struct sk_buff *buff;
struct flowi6 fl6;
- struct net *net = dev_net(skb_dst(skb)->dev);
+ struct net *net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
struct sock *ctl_sk = net->ipv6.tcp_sk;
unsigned int tot_len = sizeof(struct tcphdr);
struct dst_entry *dst;
@@ -946,7 +946,7 @@ static void tcp_v6_send_reset(struct soc
(th->doff << 2);

oif = sk ? sk->sk_bound_dev_if : 0;
- tcp_v6_send_response(skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);
+ tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);

#ifdef CONFIG_TCP_MD5SIG
release_sk1:
@@ -957,13 +957,13 @@ release_sk1:
#endif
}

-static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
- u32 win, u32 tsval, u32 tsecr, int oif,
+static void tcp_v6_send_ack(struct sock *sk, struct sk_buff *skb, u32 seq,
+ u32 ack, u32 win, u32 tsval, u32 tsecr, int oif,
struct tcp_md5sig_key *key, u8 tclass,
u32 label)
{
- tcp_v6_send_response(skb, seq, ack, win, tsval, tsecr, oif, key, 0, tclass,
- label);
+ tcp_v6_send_response(sk, skb, seq, ack, win, tsval, tsecr, oif, key, 0,
+ tclass, label);
}

static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
@@ -971,7 +971,7 @@ static void tcp_v6_timewait_ack(struct s
struct inet_timewait_sock *tw = inet_twsk(sk);
struct tcp_timewait_sock *tcptw = tcp_twsk(sk);

- tcp_v6_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
+ tcp_v6_send_ack(sk, skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
tcp_time_stamp + tcptw->tw_ts_offset,
tcptw->tw_ts_recent, tw->tw_bound_dev_if, tcp_twsk_md5_key(tcptw),
@@ -986,10 +986,10 @@ static void tcp_v6_reqsk_send_ack(struct
/* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
* sk->sk_state == TCP_SYN_RECV -> for Fast Open.
*/
- tcp_v6_send_ack(skb, (sk->sk_state == TCP_LISTEN) ?
+ tcp_v6_send_ack(sk, skb, (sk->sk_state == TCP_LISTEN) ?
tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
- tcp_rsk(req)->rcv_nxt,
- req->rcv_wnd, tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
+ tcp_rsk(req)->rcv_nxt, req->rcv_wnd,
+ tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
0, 0);
}



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