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ipv6: add complete rcu protection around np->opt

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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@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-11-29 19:37:57 -08:00 committed by David S. Miller
parent 01b3f52157
commit 45f6fad84c
13 changed files with 122 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/ipv6.h
View File

@ -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;

21
include/net/ipv6.h
View File

@ -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,

33
net/dccp/ipv6.c
View File

@ -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;

13
net/ipv6/af_inet6.c
View File

@ -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)) {

4
net/ipv6/datagram.c
View File

@ -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;

3
net/ipv6/exthdrs.c
View File

@ -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);

11
net/ipv6/inet6_connection_sock.c
View File

@ -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;
}

33
net/ipv6/ipv6_sockglue.c
View File

@ -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 @@ 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 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)

8
net/ipv6/raw.c
View File

@ -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 @@ done:
dst_release(dst);
out:
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
return err < 0 ? err : len;
do_confirm:
dst_confirm(dst);

2
net/ipv6/syncookies.c
View File

@ -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;

28
net/ipv6/tcp_ipv6.c
View File

@ -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);

8
net/ipv6/udp.c
View File

@ -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 @@ 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);
@ -1373,6 +1376,7 @@ release_dst:
out:
dst_release(dst);
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
if (!err)
return len;
/*

8
net/l2tp/l2tp_ip6.c
View File

@ -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 @@ done:
dst_release(dst);
out:
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
return err < 0 ? err : len;