linux-kernel - [PATCH net v6 01/10] ip6mr: Lock RCU before ip6mr_get_table() call in ip6mr_vif_seq

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Message-ID: <20241017174109.85717-2-stefan.wiehler@nokia.com>
Date: Thu, 17 Oct 2024 19:37:43 +0200
From: Stefan Wiehler <stefan.wiehler@...ia.com>
To: "David S . Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Stefan Wiehler <stefan.wiehler@...ia.com>
Subject: [PATCH net v6 01/10] ip6mr: Lock RCU before ip6mr_get_table() call in ip6mr_vif_seq_start()

When IPV6_MROUTE_MULTIPLE_TABLES is enabled, multicast routing tables
must be read under RCU or RTNL lock.

In case ip6mr_vif_seq_start() fails with an error (currently not
possible, as RT6_TABLE_DFLT always exists, ip6mr_get_table() cannot fail
in this case), ip6mr_vif_seq_stop() would be called and release the RCU
lock.

Signed-off-by: Stefan Wiehler <stefan.wiehler@...ia.com>
Fixes: d1db275dd3f6 ("ipv6: ip6mr: support multiple tables")
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/ip6mr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 76db80a7124c..3acc4c8a226d 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -411,13 +411,13 @@ static void *ip6mr_vif_seq_start(struct seq_file *seq, loff_t *pos)
 	struct net *net = seq_file_net(seq);
 	struct mr_table *mrt;
 
+	rcu_read_lock();
 	mrt = ip6mr_get_table(net, RT6_TABLE_DFLT);
 	if (!mrt)
 		return ERR_PTR(-ENOENT);
 
 	iter->mrt = mrt;
 
-	rcu_read_lock();
 	return mr_vif_seq_start(seq, pos);
 }
 
-- 
2.42.0