netdev - [PATCH net-next 3/3] neighbour: no longer hold RTNL in neigh_dump

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Message-ID: <20240418095106.3680616-4-edumazet@google.com>
Date: Thu, 18 Apr 2024 09:51:06 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, David Ahern <dsahern@...nel.org>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 3/3] neighbour: no longer hold RTNL in neigh_dump_info()

neigh_dump_table() is already relying on RCU protection.

pneigh_dump_table() is using its own protection (tbl->lock)

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/neighbour.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 2f9efc89e94e0f6d9e1491019583babb7bae77c7..13f2629091ef9ecd70a83f047a146c0990f308d9 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2721,7 +2721,6 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 	if (filter->dev_idx || filter->master_idx)
 		flags |= NLM_F_DUMP_FILTERED;
 
-	rcu_read_lock();
 	nht = rcu_dereference(tbl->nht);
 
 	for (h = s_h; h < (1 << nht->hash_shift); h++) {
@@ -2745,7 +2744,6 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 		}
 	}
 out:
-	rcu_read_unlock();
 	cb->args[1] = h;
 	cb->args[2] = idx;
 	return err;
@@ -2879,8 +2877,9 @@ static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 
 	s_t = cb->args[0];
 
+	rcu_read_lock();
 	for (t = 0; t < NEIGH_NR_TABLES; t++) {
-		tbl = rcu_dereference_rtnl(neigh_tables[t]);
+		tbl = rcu_dereference(neigh_tables[t]);
 
 		if (!tbl)
 			continue;
@@ -2896,6 +2895,7 @@ static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 		if (err < 0)
 			break;
 	}
+	rcu_read_unlock();
 
 	cb->args[0] = t;
 	return err;
@@ -3892,7 +3892,8 @@ static int __init neigh_init(void)
 {
 	rtnl_register(PF_UNSPEC, RTM_NEWNEIGH, neigh_add, NULL, 0);
 	rtnl_register(PF_UNSPEC, RTM_DELNEIGH, neigh_delete, NULL, 0);
-	rtnl_register(PF_UNSPEC, RTM_GETNEIGH, neigh_get, neigh_dump_info, 0);
+	rtnl_register(PF_UNSPEC, RTM_GETNEIGH, neigh_get, neigh_dump_info,
+		      RTNL_FLAG_DUMP_UNLOCKED);
 
 	rtnl_register(PF_UNSPEC, RTM_GETNEIGHTBL, NULL, neightbl_dump_info,
 		      0);
-- 
2.44.0.683.g7961c838ac-goog