Commit 45f6fad8 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ipv6: add complete rcu protection around np->opt

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: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 01b3f521
......@@ -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;
......
......@@ -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,
......
......@@ -202,7 +202,9 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req
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(const struct sock *sk, struct request_sock *req
&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);
}
......@@ -387,6 +392,7 @@ static struct sock *dccp_v6_request_recv_sock(const struct sock *sk,
struct inet_request_sock *ireq = inet_rsk(req);
struct ipv6_pinfo *newnp;
const struct ipv6_pinfo *np = inet6_sk(sk);
struct ipv6_txoptions *opt;
struct inet_sock *newinet;
struct dccp6_sock *newdp6;
struct sock *newsk;
......@@ -488,13 +494,15 @@ static struct sock *dccp_v6_request_recv_sock(const struct sock *sk,
* 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));
......@@ -757,6 +765,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
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;
......@@ -856,7 +865,8 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
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)) {
......@@ -876,9 +886,8 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
__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;
......
......@@ -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 *sk)
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)) {
......
......@@ -167,8 +167,10 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
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;
......
......@@ -727,6 +727,7 @@ ipv6_dup_options(struct sock *sk, struct ipv6_txoptions *opt)
*((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, struct ipv6_txoptions *opt,
return ERR_PTR(-ENOBUFS);
memset(opt2, 0, tot_len);
atomic_set(&opt2->refcnt, 1);
opt2->tot_len = tot_len;
p = (char *)(opt2 + 1);
......
......@@ -78,7 +78,9 @@ struct dst_entry *inet6_csk_route_req(const struct sock *sk,
memset(fl6, 0, sizeof(*fl6));
fl6->flowi6_proto = proto;
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;
......@@ -142,7 +144,9 @@ static struct dst_entry *inet6_csk_route_socket(struct sock *sk,
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) {
......@@ -175,7 +179,8 @@ int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl_unused
/* 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;
}
......
......@@ -111,7 +111,8 @@ struct ipv6_txoptions *ipv6_update_options(struct sock *sk,
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 sock *sk, int level, int optname,
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 sock *sk, int level, int optname,
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 sock *sk, int level, int optname,
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 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
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 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
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 sock *sk, int level, int optname,
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)
......
......@@ -733,6 +733,7 @@ static int raw6_getfrag(void *from, char *to, int offset, int len, int odd,
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;
......@@ -839,8 +840,10 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
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);
......@@ -906,6 +909,7 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
dst_release(dst);
out:
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
return err < 0 ? err : len;
do_confirm:
dst_confirm(dst);
......
......@@ -222,7 +222,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
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;
......
......@@ -120,6 +120,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
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 *sk, struct sockaddr *uaddr,
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 *sk, struct sockaddr *uaddr,
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(const struct sock *sk, struct dst_entry *dst,
if (np->repflow && ireq->pktopts)
fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts));
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);
}
......@@ -972,6 +975,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
struct inet_request_sock *ireq;
struct ipv6_pinfo *newnp;
const struct ipv6_pinfo *np = inet6_sk(sk);
struct ipv6_txoptions *opt;
struct tcp6_sock *newtcp6sk;
struct inet_sock *newinet;
struct tcp_sock *newtp;
......@@ -1098,13 +1102,15 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
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);
......
......@@ -1110,6 +1110,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
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;
......@@ -1263,8 +1264,10 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
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);
......@@ -1373,6 +1376,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
out:
dst_release(dst);
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
if (!err)
return len;
/*
......
......@@ -486,6 +486,7 @@ static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
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 *sk, struct msghdr *msg, size_t len)
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 @@ static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
dst_release(dst);
out:
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
return err < 0 ? err : len;
......
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