| Message ID | 1304539346.32152.81.camel@edumazet-laptop |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Eric Dumazet <eric.dumazet@gmail.com> Date: Wed, 04 May 2011 22:02:26 +0200 > [PATCH] net: ip_expire() must revalidate route > > Commit 4a94445c9a5c (net: Use ip_route_input_noref() in input path) > added a bug in IP defragmentation handling, in case timeout is fired. > > When a frame is defragmented, we use last skb dst field when building > final skb. Its dst is valid, since we are in rcu read section. > > But if a timeout occurs, we take first queued fragment to build one ICMP > TIME EXCEEDED message. Problem is all queued skb have weak dst pointers, > since we escaped RCU critical section after their queueing. icmp_send() > might dereference a now freed (and possibly reused) part of memory. > > Calling skb_dst_drop() and ip_route_input_noref() to revalidate route is > the only possible choice. > > Reported-by: Denys Fedoryshchenko <denys@visp.net.lb> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> > --- Applied to net-2.6 and queued up for -stable, thanks Eric! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index a1151b8..b1d282f 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -223,31 +223,30 @@ static void ip_expire(unsigned long arg) if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) { struct sk_buff *head = qp->q.fragments; + const struct iphdr *iph; + int err; rcu_read_lock(); head->dev = dev_get_by_index_rcu(net, qp->iif); if (!head->dev) goto out_rcu_unlock; + /* skb dst is stale, drop it, and perform route lookup again */ + skb_dst_drop(head); + iph = ip_hdr(head); + err = ip_route_input_noref(head, iph->daddr, iph->saddr, + iph->tos, head->dev); + if (err) + goto out_rcu_unlock; + /* - * Only search router table for the head fragment, - * when defraging timeout at PRE_ROUTING HOOK. + * Only an end host needs to send an ICMP + * "Fragment Reassembly Timeout" message, per RFC792. */ - if (qp->user == IP_DEFRAG_CONNTRACK_IN && !skb_dst(head)) { - const struct iphdr *iph = ip_hdr(head); - int err = ip_route_input(head, iph->daddr, iph->saddr, - iph->tos, head->dev); - if (unlikely(err)) - goto out_rcu_unlock; - - /* - * Only an end host needs to send an ICMP - * "Fragment Reassembly Timeout" message, per RFC792. - */ - if (skb_rtable(head)->rt_type != RTN_LOCAL) - goto out_rcu_unlock; + if (qp->user == IP_DEFRAG_CONNTRACK_IN && + skb_rtable(head)->rt_type != RTN_LOCAL) + goto out_rcu_unlock; - } /* Send an ICMP "Fragment Reassembly Timeout" message. */ icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);