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inet: add RCU protection to inet->opt

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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>
This commit is contained in:
Eric Dumazet
2011-04-21 09:45:37 +00:00
committed by David S. Miller
parent 0a14842f5a
commit f6d8bd051c
17 changed files with 241 additions and 168 deletions
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4
net/ipv4/syncookies.c
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@@ -321,10 +321,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
* the ACK carries the same options again (see RFC1122 4.2.3.8)
*/
if (opt && opt->optlen) {
int opt_size = sizeof(struct ip_options) + opt->optlen;
int opt_size = sizeof(struct ip_options_rcu) + opt->optlen;
ireq->opt = kmalloc(opt_size, GFP_ATOMIC);
if (ireq->opt != NULL && ip_options_echo(ireq->opt, skb)) {
if (ireq->opt != NULL && ip_options_echo(&ireq->opt->opt, skb)) {
kfree(ireq->opt);
ireq->opt = NULL;
}