Commit 8e3d5be7 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

ipv6: Avoid double dst_free 



It is a prep work to get dst freeing from fib tree undergo
a rcu grace period.

The following is a common paradigm:
if (ip6_del_rt(rt))
	dst_free(rt)

which means, if rt cannot be deleted from the fib tree, dst_free(rt) now.
1. We don't know the ip6_del_rt(rt) failure is because it
   was not managed by fib tree (e.g. DST_NOCACHE) or it had already been
   removed from the fib tree.
2. If rt had been managed by the fib tree, ip6_del_rt(rt) failure means
   dst_free(rt) has been called already.  A second
   dst_free(rt) is not always obviously safe.  The rt may have
   been destroyed already.
3. If rt is a DST_NOCACHE, dst_free(rt) should not be called.
4. It is a stopper to make dst freeing from fib tree undergo a
   rcu grace period.

This patch is to use a DST_NOCACHE flag to indicate a rt is
not managed by the fib tree.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent cdf3464e

net/ipv6/addrconf.c

+3 −4
Original line number Diff line number Diff line
@@ -5127,13 +5127,12 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp) 


			rt = addrconf_get_prefix_route(&ifp->peer_addr, 128,

						       ifp->idev->dev, 0, 0);

			if (rt && ip6_del_rt(rt))

				dst_free(&rt->dst);

			if (rt)

				ip6_del_rt(rt);

		}

		dst_hold(&ifp->rt->dst);



		if (ip6_del_rt(ifp->rt))

			dst_free(&ifp->rt->dst);

		ip6_del_rt(ifp->rt);



		rt_genid_bump_ipv6(net);

		break;

net/ipv6/ip6_fib.c

+9 −2
Original line number Diff line number Diff line
@@ -933,6 +933,10 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, 
	int replace_required = 0;

	int sernum = fib6_new_sernum(info->nl_net);



	if (WARN_ON_ONCE((rt->dst.flags & DST_NOCACHE) &&

			 !atomic_read(&rt->dst.__refcnt)))

		return -EINVAL;



	if (info->nlh) {

		if (!(info->nlh->nlmsg_flags & NLM_F_CREATE))

			allow_create = 0;
@@ -1025,6 +1029,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, 
		fib6_start_gc(info->nl_net, rt);

		if (!(rt->rt6i_flags & RTF_CACHE))

			fib6_prune_clones(info->nl_net, pn);

		rt->dst.flags &= ~DST_NOCACHE;

	}



out:
@@ -1049,6 +1054,7 @@ out: 
			atomic_inc(&pn->leaf->rt6i_ref);

		}

#endif

		if (!(rt->dst.flags & DST_NOCACHE))

			dst_free(&rt->dst);

	}

	return err;
@@ -1060,6 +1066,7 @@ out: 
st_failure:

	if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT)))

		fib6_repair_tree(info->nl_net, fn);

	if (!(rt->dst.flags & DST_NOCACHE))

		dst_free(&rt->dst);

	return err;

#endif

net/ipv6/route.c

+4 −3
Original line number Diff line number Diff line
@@ -1322,8 +1322,7 @@ static void ip6_link_failure(struct sk_buff *skb) 
	if (rt) {

		if (rt->rt6i_flags & RTF_CACHE) {

			dst_hold(&rt->dst);

			if (ip6_del_rt(rt))

				dst_free(&rt->dst);

			ip6_del_rt(rt);

		} else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) {

			rt->rt6i_node->fn_sernum = -1;

		}
@@ -2028,7 +2027,8 @@ static int __ip6_del_rt(struct rt6_info *rt, struct nl_info *info) 
	struct fib6_table *table;

	struct net *net = dev_net(rt->dst.dev);



	if (rt == net->ipv6.ip6_null_entry) {

	if (rt == net->ipv6.ip6_null_entry ||

	    rt->dst.flags & DST_NOCACHE) {

		err = -ENOENT;

		goto out;

	}
@@ -2515,6 +2515,7 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev, 
	rt->rt6i_dst.addr = *addr;

	rt->rt6i_dst.plen = 128;

	rt->rt6i_table = fib6_get_table(net, RT6_TABLE_LOCAL);

	rt->dst.flags |= DST_NOCACHE;



	atomic_set(&rt->dst.__refcnt, 1);

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