[PATCH 4.3 40/71] ipv6: add complete rcu protection around np->opt

From: Greg Kroah-Hartman
Date: Sat Dec 12 2015 - 15:34:55 EST

4.3-stable review patch. If anyone has any objections, please let me know.

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

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit 45f6fad84cc305103b28d73482b344d7f5b76f39 ]

This patch addresses multiple problems :

UDP/RAW sendmsg() need to get a stable struct ipv6_txoptions
while socket is not locked : Other threads can change np->opt
concurrently. Dmitry posted a syzkaller
(http://github.com/google/syzkaller) program desmonstrating
use-after-free.

Starting with TCP/DCCP lockless listeners, tcp_v6_syn_recv_sock()
and dccp_v6_request_recv_sock() also need to use RCU protection
to dereference np->opt once (before calling ipv6_dup_options())

This patch adds full RCU protection to np->opt

Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/ipv6.h | 2 +-
include/net/ipv6.h | 21 ++++++++++++++++++++-
net/dccp/ipv6.c | 33 +++++++++++++++++++++------------
net/ipv6/af_inet6.c | 13 +++++++++----
net/ipv6/datagram.c | 4 +++-
net/ipv6/exthdrs.c | 3 ++-
net/ipv6/inet6_connection_sock.c | 11 ++++++++---
net/ipv6/ipv6_sockglue.c | 33 ++++++++++++++++++++++-----------
net/ipv6/raw.c | 8 ++++++--
net/ipv6/syncookies.c | 2 +-
net/ipv6/tcp_ipv6.c | 28 +++++++++++++++++-----------
net/ipv6/udp.c | 8 ++++++--
net/l2tp/l2tp_ip6.c | 8 ++++++--
13 files changed, 122 insertions(+), 52 deletions(-)

--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -227,7 +227,7 @@ struct ipv6_pinfo {
struct ipv6_ac_socklist *ipv6_ac_list;
struct ipv6_fl_socklist __rcu *ipv6_fl_list;

- struct ipv6_txoptions *opt;
+ struct ipv6_txoptions __rcu *opt;
struct sk_buff *pktoptions;
struct sk_buff *rxpmtu;
struct inet6_cork cork;
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -205,6 +205,7 @@ extern rwlock_t ip6_ra_lock;
*/

struct ipv6_txoptions {
+ atomic_t refcnt;
/* Length of this structure */
int tot_len;

@@ -217,7 +218,7 @@ struct ipv6_txoptions {
struct ipv6_opt_hdr *dst0opt;
struct ipv6_rt_hdr *srcrt; /* Routing Header */
struct ipv6_opt_hdr *dst1opt;
-
+ struct rcu_head rcu;
/* Option buffer, as read by IPV6_PKTOPTIONS, starts here. */
};

@@ -252,6 +253,24 @@ struct ipv6_fl_socklist {
struct rcu_head rcu;
};

+static inline struct ipv6_txoptions *txopt_get(const struct ipv6_pinfo *np)
+{
+ struct ipv6_txoptions *opt;
+
+ rcu_read_lock();
+ opt = rcu_dereference(np->opt);
+ if (opt && !atomic_inc_not_zero(&opt->refcnt))
+ opt = NULL;
+ rcu_read_unlock();
+ return opt;
+}
+
+static inline void txopt_put(struct ipv6_txoptions *opt)
+{
+ if (opt && atomic_dec_and_test(&opt->refcnt))
+ kfree_rcu(opt, rcu);
+}
+
struct ip6_flowlabel *fl6_sock_lookup(struct sock *sk, __be32 label);
struct ipv6_txoptions *fl6_merge_options(struct ipv6_txoptions *opt_space,
struct ip6_flowlabel *fl,
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -202,7 +202,9 @@ static int dccp_v6_send_response(struct
security_req_classify_flow(req, flowi6_to_flowi(&fl6));


- final_p = fl6_update_dst(&fl6, np->opt, &final);
+ rcu_read_lock();
+ final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
+ rcu_read_unlock();

dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
if (IS_ERR(dst)) {
@@ -219,7 +221,10 @@ static int dccp_v6_send_response(struct
&ireq->ir_v6_loc_addr,
&ireq->ir_v6_rmt_addr);
fl6.daddr = ireq->ir_v6_rmt_addr;
- err = ip6_xmit(sk, skb, &fl6, np->opt, np->tclass);
+ rcu_read_lock();
+ err = ip6_xmit(sk, skb, &fl6, rcu_dereference(np->opt),
+ np->tclass);
+ rcu_read_unlock();
err = net_xmit_eval(err);
}

@@ -415,6 +420,7 @@ static struct sock *dccp_v6_request_recv
{
struct inet_request_sock *ireq = inet_rsk(req);
struct ipv6_pinfo *newnp, *np = inet6_sk(sk);
+ struct ipv6_txoptions *opt;
struct inet_sock *newinet;
struct dccp6_sock *newdp6;
struct sock *newsk;
@@ -534,13 +540,15 @@ static struct sock *dccp_v6_request_recv
* Yes, keeping reference count would be much more clever, but we make
* one more one thing there: reattach optmem to newsk.
*/
- if (np->opt != NULL)
- newnp->opt = ipv6_dup_options(newsk, np->opt);
-
+ opt = rcu_dereference(np->opt);
+ if (opt) {
+ opt = ipv6_dup_options(newsk, opt);
+ RCU_INIT_POINTER(newnp->opt, opt);
+ }
inet_csk(newsk)->icsk_ext_hdr_len = 0;
- if (newnp->opt != NULL)
- inet_csk(newsk)->icsk_ext_hdr_len = (newnp->opt->opt_nflen +
- newnp->opt->opt_flen);
+ if (opt)
+ inet_csk(newsk)->icsk_ext_hdr_len = opt->opt_nflen +
+ opt->opt_flen;

dccp_sync_mss(newsk, dst_mtu(dst));

@@ -793,6 +801,7 @@ static int dccp_v6_connect(struct sock *
struct ipv6_pinfo *np = inet6_sk(sk);
struct dccp_sock *dp = dccp_sk(sk);
struct in6_addr *saddr = NULL, *final_p, final;
+ struct ipv6_txoptions *opt;
struct flowi6 fl6;
struct dst_entry *dst;
int addr_type;
@@ -892,7 +901,8 @@ static int dccp_v6_connect(struct sock *
fl6.fl6_sport = inet->inet_sport;
security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

- final_p = fl6_update_dst(&fl6, np->opt, &final);
+ opt = rcu_dereference_protected(np->opt, sock_owned_by_user(sk));
+ final_p = fl6_update_dst(&fl6, opt, &final);

dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
if (IS_ERR(dst)) {
@@ -912,9 +922,8 @@ static int dccp_v6_connect(struct sock *
__ip6_dst_store(sk, dst, NULL, NULL);

icsk->icsk_ext_hdr_len = 0;
- if (np->opt != NULL)
- icsk->icsk_ext_hdr_len = (np->opt->opt_flen +
- np->opt->opt_nflen);
+ if (opt)
+ icsk->icsk_ext_hdr_len = opt->opt_flen + opt->opt_nflen;

inet->inet_dport = usin->sin6_port;

--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -428,9 +428,11 @@ void inet6_destroy_sock(struct sock *sk)

/* Free tx options */

- opt = xchg(&np->opt, NULL);
- if (opt)
- sock_kfree_s(sk, opt, opt->tot_len);
+ opt = xchg((__force struct ipv6_txoptions **)&np->opt, NULL);
+ if (opt) {
+ atomic_sub(opt->tot_len, &sk->sk_omem_alloc);
+ txopt_put(opt);
+ }
}
EXPORT_SYMBOL_GPL(inet6_destroy_sock);

@@ -659,7 +661,10 @@ int inet6_sk_rebuild_header(struct sock
fl6.fl6_sport = inet->inet_sport;
security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

- final_p = fl6_update_dst(&fl6, np->opt, &final);
+ rcu_read_lock();
+ final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt),
+ &final);
+ rcu_read_unlock();

dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
if (IS_ERR(dst)) {
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -167,8 +167,10 @@ ipv4_connected:

security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

- opt = flowlabel ? flowlabel->opt : np->opt;
+ rcu_read_lock();
+ opt = flowlabel ? flowlabel->opt : rcu_dereference(np->opt);
final_p = fl6_update_dst(&fl6, opt, &final);
+ rcu_read_unlock();

dst = ip6_dst_lookup_flow(sk, &fl6, final_p);
err = 0;
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -727,6 +727,7 @@ ipv6_dup_options(struct sock *sk, struct
*((char **)&opt2->dst1opt) += dif;
if (opt2->srcrt)
*((char **)&opt2->srcrt) += dif;
+ atomic_set(&opt2->refcnt, 1);
}
return opt2;
}
@@ -790,7 +791,7 @@ ipv6_renew_options(struct sock *sk, stru
return ERR_PTR(-ENOBUFS);

memset(opt2, 0, tot_len);
-
+ atomic_set(&opt2->refcnt, 1);
opt2->tot_len = tot_len;
p = (char *)(opt2 + 1);

--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -77,7 +77,9 @@ struct dst_entry *inet6_csk_route_req(st
memset(fl6, 0, sizeof(*fl6));
fl6->flowi6_proto = IPPROTO_TCP;
fl6->daddr = ireq->ir_v6_rmt_addr;
- final_p = fl6_update_dst(fl6, np->opt, &final);
+ rcu_read_lock();
+ final_p = fl6_update_dst(fl6, rcu_dereference(np->opt), &final);
+ rcu_read_unlock();
fl6->saddr = ireq->ir_v6_loc_addr;
fl6->flowi6_oif = ireq->ir_iif;
fl6->flowi6_mark = ireq->ir_mark;
@@ -207,7 +209,9 @@ static struct dst_entry *inet6_csk_route
fl6->fl6_dport = inet->inet_dport;
security_sk_classify_flow(sk, flowi6_to_flowi(fl6));

- final_p = fl6_update_dst(fl6, np->opt, &final);
+ rcu_read_lock();
+ final_p = fl6_update_dst(fl6, rcu_dereference(np->opt), &final);
+ rcu_read_unlock();

dst = __inet6_csk_dst_check(sk, np->dst_cookie);
if (!dst) {
@@ -240,7 +244,8 @@ int inet6_csk_xmit(struct sock *sk, stru
/* Restore final destination back after routing done */
fl6.daddr = sk->sk_v6_daddr;

- res = ip6_xmit(sk, skb, &fl6, np->opt, np->tclass);
+ res = ip6_xmit(sk, skb, &fl6, rcu_dereference(np->opt),
+ np->tclass);
rcu_read_unlock();
return res;
}
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -111,7 +111,8 @@ struct ipv6_txoptions *ipv6_update_optio
icsk->icsk_sync_mss(sk, icsk->icsk_pmtu_cookie);
}
}
- opt = xchg(&inet6_sk(sk)->opt, opt);
+ opt = xchg((__force struct ipv6_txoptions **)&inet6_sk(sk)->opt,
+ opt);
sk_dst_reset(sk);

return opt;
@@ -231,9 +232,12 @@ static int do_ipv6_setsockopt(struct soc
sk->sk_socket->ops = &inet_dgram_ops;
sk->sk_family = PF_INET;
}
- opt = xchg(&np->opt, NULL);
- if (opt)
- sock_kfree_s(sk, opt, opt->tot_len);
+ opt = xchg((__force struct ipv6_txoptions **)&np->opt,
+ NULL);
+ if (opt) {
+ atomic_sub(opt->tot_len, &sk->sk_omem_alloc);
+ txopt_put(opt);
+ }
pktopt = xchg(&np->pktoptions, NULL);
kfree_skb(pktopt);

@@ -403,7 +407,8 @@ static int do_ipv6_setsockopt(struct soc
if (optname != IPV6_RTHDR && !ns_capable(net->user_ns, CAP_NET_RAW))
break;

- opt = ipv6_renew_options(sk, np->opt, optname,
+ opt = rcu_dereference_protected(np->opt, sock_owned_by_user(sk));
+ opt = ipv6_renew_options(sk, opt, optname,
(struct ipv6_opt_hdr __user *)optval,
optlen);
if (IS_ERR(opt)) {
@@ -432,8 +437,10 @@ static int do_ipv6_setsockopt(struct soc
retv = 0;
opt = ipv6_update_options(sk, opt);
sticky_done:
- if (opt)
- sock_kfree_s(sk, opt, opt->tot_len);
+ if (opt) {
+ atomic_sub(opt->tot_len, &sk->sk_omem_alloc);
+ txopt_put(opt);
+ }
break;
}

@@ -486,6 +493,7 @@ sticky_done:
break;

memset(opt, 0, sizeof(*opt));
+ atomic_set(&opt->refcnt, 1);
opt->tot_len = sizeof(*opt) + optlen;
retv = -EFAULT;
if (copy_from_user(opt+1, optval, optlen))
@@ -502,8 +510,10 @@ update:
retv = 0;
opt = ipv6_update_options(sk, opt);
done:
- if (opt)
- sock_kfree_s(sk, opt, opt->tot_len);
+ if (opt) {
+ atomic_sub(opt->tot_len, &sk->sk_omem_alloc);
+ txopt_put(opt);
+ }
break;
}
case IPV6_UNICAST_HOPS:
@@ -1110,10 +1120,11 @@ static int do_ipv6_getsockopt(struct soc
case IPV6_RTHDR:
case IPV6_DSTOPTS:
{
+ struct ipv6_txoptions *opt;

lock_sock(sk);
- len = ipv6_getsockopt_sticky(sk, np->opt,
- optname, optval, len);
+ opt = rcu_dereference_protected(np->opt, sock_owned_by_user(sk));
+ len = ipv6_getsockopt_sticky(sk, opt, optname, optval, len);
release_sock(sk);
/* check if ipv6_getsockopt_sticky() returns err code */
if (len < 0)
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -732,6 +732,7 @@ static int raw6_getfrag(void *from, char

static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
+ struct ipv6_txoptions *opt_to_free = NULL;
struct ipv6_txoptions opt_space;
DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
struct in6_addr *daddr, *final_p, final;
@@ -838,8 +839,10 @@ static int rawv6_sendmsg(struct sock *sk
if (!(opt->opt_nflen|opt->opt_flen))
opt = NULL;
}
- if (!opt)
- opt = np->opt;
+ if (!opt) {
+ opt = txopt_get(np);
+ opt_to_free = opt;
+ }
if (flowlabel)
opt = fl6_merge_options(&opt_space, flowlabel, opt);
opt = ipv6_fixup_options(&opt_space, opt);
@@ -905,6 +908,7 @@ done:
dst_release(dst);
out:
fl6_sock_release(flowlabel);
+ txopt_put(opt_to_free);
return err < 0 ? err : len;
do_confirm:
dst_confirm(dst);
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -225,7 +225,7 @@ struct sock *cookie_v6_check(struct sock
memset(&fl6, 0, sizeof(fl6));
fl6.flowi6_proto = IPPROTO_TCP;
fl6.daddr = ireq->ir_v6_rmt_addr;
- final_p = fl6_update_dst(&fl6, np->opt, &final);
+ final_p = fl6_update_dst(&fl6, rcu_dereference(np->opt), &final);
fl6.saddr = ireq->ir_v6_loc_addr;
fl6.flowi6_oif = sk->sk_bound_dev_if;
fl6.flowi6_mark = ireq->ir_mark;
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -120,6 +120,7 @@ static int tcp_v6_connect(struct sock *s
struct ipv6_pinfo *np = inet6_sk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct in6_addr *saddr = NULL, *final_p, final;
+ struct ipv6_txoptions *opt;
struct flowi6 fl6;
struct dst_entry *dst;
int addr_type;
@@ -235,7 +236,8 @@ static int tcp_v6_connect(struct sock *s
fl6.fl6_dport = usin->sin6_port;
fl6.fl6_sport = inet->inet_sport;

- final_p = fl6_update_dst(&fl6, np->opt, &final);
+ opt = rcu_dereference_protected(np->opt, sock_owned_by_user(sk));
+ final_p = fl6_update_dst(&fl6, opt, &final);

security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

@@ -263,9 +265,9 @@ static int tcp_v6_connect(struct sock *s
tcp_fetch_timewait_stamp(sk, dst);

icsk->icsk_ext_hdr_len = 0;
- if (np->opt)
- icsk->icsk_ext_hdr_len = (np->opt->opt_flen +
- np->opt->opt_nflen);
+ if (opt)
+ icsk->icsk_ext_hdr_len = opt->opt_flen +
+ opt->opt_nflen;

tp->rx_opt.mss_clamp = IPV6_MIN_MTU - sizeof(struct tcphdr) - sizeof(struct ipv6hdr);

@@ -461,7 +463,8 @@ static int tcp_v6_send_synack(struct soc
fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts));

skb_set_queue_mapping(skb, queue_mapping);
- err = ip6_xmit(sk, skb, fl6, np->opt, np->tclass);
+ err = ip6_xmit(sk, skb, fl6, rcu_dereference(np->opt),
+ np->tclass);
err = net_xmit_eval(err);
}

@@ -991,6 +994,7 @@ static struct sock *tcp_v6_syn_recv_sock
struct inet_request_sock *ireq;
struct ipv6_pinfo *newnp, *np = inet6_sk(sk);
struct tcp6_sock *newtcp6sk;
+ struct ipv6_txoptions *opt;
struct inet_sock *newinet;
struct tcp_sock *newtp;
struct sock *newsk;
@@ -1126,13 +1130,15 @@ static struct sock *tcp_v6_syn_recv_sock
but we make one more one thing there: reattach optmem
to newsk.
*/
- if (np->opt)
- newnp->opt = ipv6_dup_options(newsk, np->opt);
-
+ opt = rcu_dereference(np->opt);
+ if (opt) {
+ opt = ipv6_dup_options(newsk, opt);
+ RCU_INIT_POINTER(newnp->opt, opt);
+ }
inet_csk(newsk)->icsk_ext_hdr_len = 0;
- if (newnp->opt)
- inet_csk(newsk)->icsk_ext_hdr_len = (newnp->opt->opt_nflen +
- newnp->opt->opt_flen);
+ if (opt)
+ inet_csk(newsk)->icsk_ext_hdr_len = opt->opt_nflen +
+ opt->opt_flen;

tcp_ca_openreq_child(newsk, dst);

--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1107,6 +1107,7 @@ int udpv6_sendmsg(struct sock *sk, struc
DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
struct in6_addr *daddr, *final_p, final;
struct ipv6_txoptions *opt = NULL;
+ struct ipv6_txoptions *opt_to_free = NULL;
struct ip6_flowlabel *flowlabel = NULL;
struct flowi6 fl6;
struct dst_entry *dst;
@@ -1260,8 +1261,10 @@ do_udp_sendmsg:
opt = NULL;
connected = 0;
}
- if (!opt)
- opt = np->opt;
+ if (!opt) {
+ opt = txopt_get(np);
+ opt_to_free = opt;
+ }
if (flowlabel)
opt = fl6_merge_options(&opt_space, flowlabel, opt);
opt = ipv6_fixup_options(&opt_space, opt);
@@ -1370,6 +1373,7 @@ release_dst:
out:
dst_release(dst);
fl6_sock_release(flowlabel);
+ txopt_put(opt_to_free);
if (!err)
return len;
/*
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -486,6 +486,7 @@ static int l2tp_ip6_sendmsg(struct sock
DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
struct in6_addr *daddr, *final_p, final;
struct ipv6_pinfo *np = inet6_sk(sk);
+ struct ipv6_txoptions *opt_to_free = NULL;
struct ipv6_txoptions *opt = NULL;
struct ip6_flowlabel *flowlabel = NULL;
struct dst_entry *dst = NULL;
@@ -575,8 +576,10 @@ static int l2tp_ip6_sendmsg(struct sock
opt = NULL;
}

- if (opt == NULL)
- opt = np->opt;
+ if (!opt) {
+ opt = txopt_get(np);
+ opt_to_free = opt;
+ }
if (flowlabel)
opt = fl6_merge_options(&opt_space, flowlabel, opt);
opt = ipv6_fixup_options(&opt_space, opt);
@@ -631,6 +634,7 @@ done:
dst_release(dst);
out:
fl6_sock_release(flowlabel);
+ txopt_put(opt_to_free);

return err < 0 ? err : len;



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