[PATCH v1 net-next 06/15] ipmr: Convert ipmr_rtm_dumproute() to RCU.

[Kuniyuki Iwashima <kuniyu@google.com>]

ipmr_rtm_dumproute() calls mr_table_dump() or mr_rtm_dumproute(),
and mr_rtm_dumproute() finally calls mr_table_dump().

mr_table_dump() calls the passed function, _ipmr_fill_mroute().

_ipmr_fill_mroute() is a wrapper of ipmr_fill_mroute() to cast
struct mr_mfc * to struct mfc_cache *.

ipmr_fill_mroute() can be already called safely under RCU.

Let's convert ipmr_rtm_dumproute() to RCU.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/ipv4/ipmr.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 53dda438ba32..3af6b3d33cc8 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -2736,15 +2736,17 @@ static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 static int ipmr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct fib_dump_filter filter = {
-		.rtnl_held = true,
+		.rtnl_held = false,
 	};
 	int err;
 
+	rcu_read_lock();
+
 	if (cb->strict_check) {
 		err = ip_valid_fib_dump_req(sock_net(skb->sk), cb->nlh,
 					    &filter, cb);
 		if (err < 0)
-			return err;
+			goto out;
 	}
 
 	if (filter.table_id) {
@@ -2752,19 +2754,28 @@ static int ipmr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
 
 		mrt = __ipmr_get_table(sock_net(skb->sk), filter.table_id);
 		if (!mrt) {
-			if (rtnl_msg_family(cb->nlh) != RTNL_FAMILY_IPMR)
-				return skb->len;
+			if (rtnl_msg_family(cb->nlh) != RTNL_FAMILY_IPMR) {
+				err = skb->len;
+				goto out;
+			}
 
 			NL_SET_ERR_MSG(cb->extack, "ipv4: MR table does not exist");
-			return -ENOENT;
+			err = -ENOENT;
+			goto out;
 		}
+
 		err = mr_table_dump(mrt, skb, cb, _ipmr_fill_mroute,
 				    &mfc_unres_lock, &filter);
-		return skb->len ? : err;
+		err = skb->len ? : err;
+		goto out;
 	}
 
-	return mr_rtm_dumproute(skb, cb, ipmr_mr_table_iter,
-				_ipmr_fill_mroute, &mfc_unres_lock, &filter);
+	err = mr_rtm_dumproute(skb, cb, ipmr_mr_table_iter,
+			       _ipmr_fill_mroute, &mfc_unres_lock, &filter);
+out:
+	rcu_read_unlock();
+
+	return err;
 }
 
 static const struct nla_policy rtm_ipmr_policy[RTA_MAX + 1] = {
@@ -3299,7 +3310,7 @@ static const struct rtnl_msg_handler ipmr_rtnl_msg_handlers[] __initconst = {
 	 .doit = ipmr_rtm_route},
 	{.protocol = RTNL_FAMILY_IPMR, .msgtype = RTM_GETROUTE,
 	 .doit = ipmr_rtm_getroute, .dumpit = ipmr_rtm_dumproute,
-	 .flags = RTNL_FLAG_DOIT_UNLOCKED},
+	 .flags = RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
 };
 
 int __init ip_mr_init(void)
-- 
2.53.0.414.gf7e9f6c205-goog