netdev - [PATCH net v6 09/10] ip6mr: Lock RCU before ip6mr_get_table() call in ip6mr_rtm

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Message-ID: <20241017174109.85717-10-stefan.wiehler@nokia.com>
Date: Thu, 17 Oct 2024 19:37:51 +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 09/10] ip6mr: Lock RCU before ip6mr_get_table() call in ip6mr_rtm_getroute()

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

Fixes: d1db275dd3f6 ("ipv6: ip6mr: support multiple tables")
Signed-off-by: Stefan Wiehler <stefan.wiehler@...ia.com>
---
 net/ipv6/ip6mr.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index b169b27de7e1..39aac81a30f1 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -2633,27 +2633,31 @@ static int ip6mr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 		grp = nla_get_in6_addr(tb[RTA_DST]);
 	tableid = tb[RTA_TABLE] ? nla_get_u32(tb[RTA_TABLE]) : 0;
 
+	rcu_read_lock();
 	mrt = ip6mr_get_table(net, tableid ?: RT_TABLE_DEFAULT);
 	if (!mrt) {
+		rcu_read_unlock();
 		NL_SET_ERR_MSG_MOD(extack, "MR table does not exist");
 		return -ENOENT;
 	}
 
 	/* entries are added/deleted only under RTNL */
-	rcu_read_lock();
 	cache = ip6mr_cache_find(mrt, &src, &grp);
-	rcu_read_unlock();
 	if (!cache) {
+		rcu_read_unlock();
 		NL_SET_ERR_MSG_MOD(extack, "MR cache entry not found");
 		return -ENOENT;
 	}
 
 	skb = nlmsg_new(mr6_msgsize(false, mrt->maxvif), GFP_KERNEL);
-	if (!skb)
+	if (!skb) {
+		rcu_read_unlock();
 		return -ENOBUFS;
+	}
 
 	err = ip6mr_fill_mroute(mrt, skb, NETLINK_CB(in_skb).portid,
 				nlh->nlmsg_seq, cache, RTM_NEWROUTE, 0);
+	rcu_read_unlock();
 	if (err < 0) {
 		kfree_skb(skb);
 		return err;
-- 
2.42.0