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: 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>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 0ef2a97..402753b 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -227,7 +227,7 @@
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;
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index ea5a13e..9a5c9f0 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -205,6 +205,7 @@
*/
struct ipv6_txoptions {
+ atomic_t refcnt;
/* Length of this structure */
int tot_len;
@@ -217,7 +218,7 @@
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 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,