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/dccp/ipv4.c b/net/dccp/ipv4.c
index b92ab65..cbbcc6c 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -48,6 +48,7 @@
struct flowi4 fl4;
struct rtable *rt;
int err;
+ struct ip_options_rcu *inet_opt;
dp->dccps_role = DCCP_ROLE_CLIENT;
@@ -58,10 +59,13 @@
return -EAFNOSUPPORT;
nexthop = daddr = usin->sin_addr.s_addr;
- if (inet->opt != NULL && inet->opt->srr) {
+
+ inet_opt = rcu_dereference_protected(inet->inet_opt,
+ sock_owned_by_user(sk));
+ if (inet_opt != NULL && inet_opt->opt.srr) {
if (daddr == 0)
return -EINVAL;
- nexthop = inet->opt->faddr;
+ nexthop = inet_opt->opt.faddr;
}
orig_sport = inet->inet_sport;
@@ -78,7 +82,7 @@
return -ENETUNREACH;
}
- if (inet->opt == NULL || !inet->opt->srr)
+ if (inet_opt == NULL || !inet_opt->opt.srr)
daddr = rt->rt_dst;
if (inet->inet_saddr == 0)
@@ -89,8 +93,8 @@
inet->inet_daddr = daddr;
inet_csk(sk)->icsk_ext_hdr_len = 0;
- if (inet->opt != NULL)
- inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
+ if (inet_opt)
+ inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
/*
* Socket identity is still unknown (sport may be zero).
* However we set state to DCCP_REQUESTING and not releasing socket
@@ -405,7 +409,7 @@
newinet->inet_daddr = ireq->rmt_addr;
newinet->inet_rcv_saddr = ireq->loc_addr;
newinet->inet_saddr = ireq->loc_addr;
- newinet->opt = ireq->opt;
+ newinet->inet_opt = ireq->opt;
ireq->opt = NULL;
newinet->mc_index = inet_iif(skb);
newinet->mc_ttl = ip_hdr(skb)->ttl;