From f6d8bd051c391c1c0458a30b2a7abcd939329259 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 21 Apr 2011 09:45:37 +0000 Subject: 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 Cc: Herbert Xu Signed-off-by: David S. Miller --- net/l2tp/l2tp_ip.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'net/l2tp/l2tp_ip.c') diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c index cc673677c5de..962a607b51da 100644 --- a/net/l2tp/l2tp_ip.c +++ b/net/l2tp/l2tp_ip.c @@ -416,7 +416,6 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m int rc; struct l2tp_ip_sock *lsa = l2tp_ip_sk(sk); struct inet_sock *inet = inet_sk(sk); - struct ip_options *opt = inet->opt; struct rtable *rt = NULL; int connected = 0; __be32 daddr; @@ -471,9 +470,14 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m rt = (struct rtable *) __sk_dst_check(sk, 0); if (rt == NULL) { + struct ip_options_rcu *inet_opt; + + inet_opt = rcu_dereference_protected(inet->inet_opt, + sock_owned_by_user(sk)); + /* Use correct destination address if we have options. */ - if (opt && opt->srr) - daddr = opt->faddr; + if (inet_opt && inet_opt->opt.srr) + daddr = inet_opt->opt.faddr; /* If this fails, retransmit mechanism of transport layer will * keep trying until route appears or the connection times -- cgit v1.2.1