netdev - [PATCH net-next 4/5] ipmr: use READ_ONCE() to read net->ipv[46].ipmr

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Message-ID: <20241009184405.3752829-5-edumazet@google.com>
Date: Wed,  9 Oct 2024 18:44:04 +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: David Ahern <dsahern@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, Jiri Pirko <jiri@...nulli.us>, 
	netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 4/5] ipmr: use READ_ONCE() to read net->ipv[46].ipmr_seq

mr_call_vif_notifiers() and mr_call_mfc_notifiers() already
uses WRITE_ONCE() on the write side.

Using RTNL to protect the reads seems a big hammer.

Constify 'struct net' argument of ip6mr_rules_seq_read()
and ipmr_rules_seq_read().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/ipmr.c  | 8 +++-----
 net/ipv6/ip6mr.c | 8 +++-----
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 089864c6a35eec146a1ba90c22d79245f8e48158..35ed0316518424c7742a93bd72d56295e1eb01aa 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -288,7 +288,7 @@ static int ipmr_rules_dump(struct net *net, struct notifier_block *nb,
 	return fib_rules_dump(net, nb, RTNL_FAMILY_IPMR, extack);
 }
 
-static unsigned int ipmr_rules_seq_read(struct net *net)
+static unsigned int ipmr_rules_seq_read(const struct net *net)
 {
 	return fib_rules_seq_read(net, RTNL_FAMILY_IPMR);
 }
@@ -346,7 +346,7 @@ static int ipmr_rules_dump(struct net *net, struct notifier_block *nb,
 	return 0;
 }
 
-static unsigned int ipmr_rules_seq_read(struct net *net)
+static unsigned int ipmr_rules_seq_read(const struct net *net)
 {
 	return 0;
 }
@@ -3037,9 +3037,7 @@ static const struct net_protocol pim_protocol = {
 
 static unsigned int ipmr_seq_read(struct net *net)
 {
-	ASSERT_RTNL();
-
-	return net->ipv4.ipmr_seq + ipmr_rules_seq_read(net);
+	return READ_ONCE(net->ipv4.ipmr_seq) + ipmr_rules_seq_read(net);
 }
 
 static int ipmr_dump(struct net *net, struct notifier_block *nb,
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 2ce4ae0d8dc3b443986d7a7b4177a057f5affaec..3f9501fd8c1ae583d4862128e8620ce6cc114d25 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -276,7 +276,7 @@ static int ip6mr_rules_dump(struct net *net, struct notifier_block *nb,
 	return fib_rules_dump(net, nb, RTNL_FAMILY_IP6MR, extack);
 }
 
-static unsigned int ip6mr_rules_seq_read(struct net *net)
+static unsigned int ip6mr_rules_seq_read(const struct net *net)
 {
 	return fib_rules_seq_read(net, RTNL_FAMILY_IP6MR);
 }
@@ -335,7 +335,7 @@ static int ip6mr_rules_dump(struct net *net, struct notifier_block *nb,
 	return 0;
 }
 
-static unsigned int ip6mr_rules_seq_read(struct net *net)
+static unsigned int ip6mr_rules_seq_read(const struct net *net)
 {
 	return 0;
 }
@@ -1262,9 +1262,7 @@ static int ip6mr_device_event(struct notifier_block *this,
 
 static unsigned int ip6mr_seq_read(struct net *net)
 {
-	ASSERT_RTNL();
-
-	return net->ipv6.ipmr_seq + ip6mr_rules_seq_read(net);
+	return READ_ONCE(net->ipv6.ipmr_seq) + ip6mr_rules_seq_read(net);
 }
 
 static int ip6mr_dump(struct net *net, struct notifier_block *nb,
-- 
2.47.0.rc0.187.ge670bccf7e-goog