inet: add RCU protection to inet->opt
We lack proper synchronization to manipulate inet->opt ip_options
Problem is ip_make_skb() calls ip_setup_cork() and
ip_setup_cork() possibly makes a copy of ipc->opt (struct ip_options),
without any protection against another thread manipulating inet->opt.
Another thread can change inet->opt pointer and free old one under us.
Use RCU to protect inet->opt (changed to inet->inet_opt).
Instead of handling atomic refcounts, just copy ip_options when
necessary, to avoid cache line dirtying.
We cant insert an rcu_head in struct ip_options since its included in
skb->cb[], so this patch is large because I had to introduce a new
ip_options_rcu structure.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 9640900..ab0c9ef 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -451,6 +451,11 @@
}
+static void opt_kfree_rcu(struct rcu_head *head)
+{
+ kfree(container_of(head, struct ip_options_rcu, rcu));
+}
+
/*
* Socket option code for IP. This is the end of the line after any
* TCP,UDP etc options on an IP socket.
@@ -497,13 +502,16 @@
switch (optname) {
case IP_OPTIONS:
{
- struct ip_options *opt = NULL;
+ struct ip_options_rcu *old, *opt = NULL;
+
if (optlen > 40)
goto e_inval;
err = ip_options_get_from_user(sock_net(sk), &opt,
optval, optlen);
if (err)
break;
+ old = rcu_dereference_protected(inet->inet_opt,
+ sock_owned_by_user(sk));
if (inet->is_icsk) {
struct inet_connection_sock *icsk = inet_csk(sk);
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
@@ -512,17 +520,18 @@
(TCPF_LISTEN | TCPF_CLOSE)) &&
inet->inet_daddr != LOOPBACK4_IPV6)) {
#endif
- if (inet->opt)
- icsk->icsk_ext_hdr_len -= inet->opt->optlen;
+ if (old)
+ icsk->icsk_ext_hdr_len -= old->opt.optlen;
if (opt)
- icsk->icsk_ext_hdr_len += opt->optlen;
+ icsk->icsk_ext_hdr_len += opt->opt.optlen;
icsk->icsk_sync_mss(sk, icsk->icsk_pmtu_cookie);
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
}
#endif
}
- opt = xchg(&inet->opt, opt);
- kfree(opt);
+ rcu_assign_pointer(inet->inet_opt, opt);
+ if (old)
+ call_rcu(&old->rcu, opt_kfree_rcu);
break;
}
case IP_PKTINFO:
@@ -1081,12 +1090,16 @@
case IP_OPTIONS:
{
unsigned char optbuf[sizeof(struct ip_options)+40];
- struct ip_options * opt = (struct ip_options *)optbuf;
+ struct ip_options *opt = (struct ip_options *)optbuf;
+ struct ip_options_rcu *inet_opt;
+
+ inet_opt = rcu_dereference_protected(inet->inet_opt,
+ sock_owned_by_user(sk));
opt->optlen = 0;
- if (inet->opt)
- memcpy(optbuf, inet->opt,
- sizeof(struct ip_options)+
- inet->opt->optlen);
+ if (inet_opt)
+ memcpy(optbuf, &inet_opt->opt,
+ sizeof(struct ip_options) +
+ inet_opt->opt.optlen);
release_sock(sk);
if (opt->optlen == 0)