[PATCH v1 net-next 06/13] ipv6: Split ip6_route_info_create().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

We will get rid of RTNL from RTM_NEWROUTE and SIOCADDRT.

Then, we want to allocate everything as possible before entering
the RCU section.

The RCU section will start in the middle of ip6_route_info_create(),
and this is problematic for ip6_route_multipath_add() that calls
ip6_route_info_create() multiple times.

Let's split ip6_route_info_create() into two parts; one for memory
allocation and another for nexthop setup.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/ipv6/route.c | 95 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 62 insertions(+), 33 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 28d38282a19e..6299cfd9f12a 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3694,15 +3694,13 @@ void fib6_nh_release_dsts(struct fib6_nh *fib6_nh)
 }
 
 static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
-					      gfp_t gfp_flags,
-					      struct netlink_ext_ack *extack)
+					       gfp_t gfp_flags,
+					       struct netlink_ext_ack *extack)
 {
 	struct net *net = cfg->fc_nlinfo.nl_net;
-	struct fib6_info *rt = NULL;
 	struct fib6_table *table;
-	struct fib6_nh *fib6_nh;
-	int err = -ENOBUFS;
-	int addr_type;
+	struct fib6_info *rt;
+	int err;
 
 	if (cfg->fc_nlinfo.nlh &&
 	    !(cfg->fc_nlinfo.nlh->nlmsg_flags & NLM_F_CREATE)) {
@@ -3714,22 +3712,22 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 	} else {
 		table = fib6_new_table(net, cfg->fc_table);
 	}
+	if (!table) {
+		err = -ENOBUFS;
+		goto err;
+	}
 
-	if (!table)
-		goto out;
-
-	err = -ENOMEM;
 	rt = fib6_info_alloc(gfp_flags, !cfg->fc_nh_id);
-	if (!rt)
-		goto out;
+	if (!rt) {
+		err = -ENOMEM;
+		goto err;
+	}
 
 	rt->fib6_metrics = ip_fib_metrics_init(cfg->fc_mx, cfg->fc_mx_len,
 					       extack);
 	if (IS_ERR(rt->fib6_metrics)) {
 		err = PTR_ERR(rt->fib6_metrics);
-		/* Do not leave garbage there. */
-		rt->fib6_metrics = (struct dst_metrics *)&dst_default_metrics;
-		goto out_free;
+		goto free;
 	}
 
 	if (cfg->fc_flags & RTF_ADDRCONF)
@@ -3737,12 +3735,12 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 
 	if (cfg->fc_flags & RTF_EXPIRES)
 		fib6_set_expires(rt, jiffies +
-				clock_t_to_jiffies(cfg->fc_expires));
+				 clock_t_to_jiffies(cfg->fc_expires));
 
 	if (cfg->fc_protocol == RTPROT_UNSPEC)
 		cfg->fc_protocol = RTPROT_BOOT;
-	rt->fib6_protocol = cfg->fc_protocol;
 
+	rt->fib6_protocol = cfg->fc_protocol;
 	rt->fib6_table = table;
 	rt->fib6_metric = cfg->fc_metric;
 	rt->fib6_type = cfg->fc_type ? : RTN_UNICAST;
@@ -3755,6 +3753,20 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 	ipv6_addr_prefix(&rt->fib6_src.addr, &cfg->fc_src, cfg->fc_src_len);
 	rt->fib6_src.plen = cfg->fc_src_len;
 #endif
+	return rt;
+free:
+	kfree(rt);
+err:
+	return ERR_PTR(err);
+}
+
+static int ip6_route_info_create_nh(struct fib6_info *rt,
+				    struct fib6_config *cfg,
+				    struct netlink_ext_ack *extack)
+{
+	struct net *net = cfg->fc_nlinfo.nl_net;
+	struct fib6_nh *fib6_nh;
+	int err;
 
 	if (cfg->fc_nh_id) {
 		struct nexthop *nh;
@@ -3779,9 +3791,11 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 		rt->nh = nh;
 		fib6_nh = nexthop_fib6_nh(rt->nh);
 	} else {
-		err = fib6_nh_init(net, rt->fib6_nh, cfg, gfp_flags, extack);
+		int addr_type;
+
+		err = fib6_nh_init(net, rt->fib6_nh, cfg, GFP_ATOMIC, extack);
 		if (err)
-			goto out;
+			goto out_release;
 
 		fib6_nh = rt->fib6_nh;
 
@@ -3800,21 +3814,20 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 		if (!ipv6_chk_addr(net, &cfg->fc_prefsrc, dev, 0)) {
 			NL_SET_ERR_MSG(extack, "Invalid source address");
 			err = -EINVAL;
-			goto out;
+			goto out_release;
 		}
 		rt->fib6_prefsrc.addr = cfg->fc_prefsrc;
 		rt->fib6_prefsrc.plen = 128;
-	} else
-		rt->fib6_prefsrc.plen = 0;
+	}
 
-	return rt;
-out:
+	return 0;
+out_release:
 	fib6_info_release(rt);
-	return ERR_PTR(err);
+	return err;
 out_free:
 	ip_fib_metrics_put(rt->fib6_metrics);
 	kfree(rt);
-	return ERR_PTR(err);
+	return err;
 }
 
 int ip6_route_add(struct fib6_config *cfg, gfp_t gfp_flags,
@@ -3827,6 +3840,10 @@ int ip6_route_add(struct fib6_config *cfg, gfp_t gfp_flags,
 	if (IS_ERR(rt))
 		return PTR_ERR(rt);
 
+	err = ip6_route_info_create_nh(rt, cfg, extack);
+	if (err)
+		return err;
+
 	err = __ip6_ins_rt(rt, &cfg->fc_nlinfo, extack);
 	fib6_info_release(rt);
 
@@ -4550,6 +4567,7 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
 		.fc_ignore_dev_down = true,
 	};
 	struct fib6_info *f6i;
+	int err;
 
 	if (anycast) {
 		cfg.fc_type = RTN_ANYCAST;
@@ -4560,14 +4578,19 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
 	}
 
 	f6i = ip6_route_info_create(&cfg, gfp_flags, extack);
-	if (!IS_ERR(f6i)) {
-		f6i->dst_nocount = true;
+	if (IS_ERR(f6i))
+		return f6i;
 
-		if (!anycast &&
-		    (READ_ONCE(net->ipv6.devconf_all->disable_policy) ||
-		     READ_ONCE(idev->cnf.disable_policy)))
-			f6i->dst_nopolicy = true;
-	}
+	err = ip6_route_info_create_nh(f6i, &cfg, extack);
+	if (err)
+		return ERR_PTR(err);
+
+	f6i->dst_nocount = true;
+
+	if (!anycast &&
+	    (READ_ONCE(net->ipv6.devconf_all->disable_policy) ||
+	     READ_ONCE(idev->cnf.disable_policy)))
+		f6i->dst_nopolicy = true;
 
 	return f6i;
 }
@@ -5365,6 +5388,12 @@ static int ip6_route_multipath_add(struct fib6_config *cfg,
 			goto cleanup;
 		}
 
+		err = ip6_route_info_create_nh(rt, &r_cfg, extack);
+		if (err) {
+			rt = NULL;
+			goto cleanup;
+		}
+
 		rt->fib6_nh->fib_nh_weight = rtnh->rtnh_hops + 1;
 
 		err = ip6_route_info_append(info->nl_net, &rt6_nh_list,
-- 
2.48.1