From: Kuniyuki Iwashima <kuniyu@google.com>
Date: Wed, 2 Jul 2025 23:01:22 +0000 (-0700)
Subject: ipv6: mcast: Use in6_dev_get() in ipv6_dev_mc_dec().
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e01b193e0b50ae849bf60067e111446f19ee2f20;p=thirdparty%2Fkernel%2Fstable.git

ipv6: mcast: Use in6_dev_get() in ipv6_dev_mc_dec().

As well as __ipv6_dev_mc_inc(), all code in __ipv6_dev_mc_dec() are
protected by inet6_dev->mc_lock, and RTNL is not needed.

Let's use in6_dev_get() in ipv6_dev_mc_dec() and remove ASSERT_RTNL()
in __ipv6_dev_mc_dec().

Now, we can remove the RTNL comment above addrconf_leave_solict() too.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250702230210.3115355-6-kuni1840@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index dcc07767e51f..8451014457dd 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2241,12 +2241,11 @@ void addrconf_join_solict(struct net_device *dev, const struct in6_addr *addr)
 	ipv6_dev_mc_inc(dev, &maddr);
 }
 
-/* caller must hold RTNL */
 void addrconf_leave_solict(struct inet6_dev *idev, const struct in6_addr *addr)
 {
 	struct in6_addr maddr;
 
-	if (idev->dev->flags&(IFF_LOOPBACK|IFF_NOARP))
+	if (READ_ONCE(idev->dev->flags) & (IFF_LOOPBACK | IFF_NOARP))
 		return;
 
 	addrconf_addr_solict_mult(addr, &maddr);
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index aa1280df4c1f..b3f063b5ffd7 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1004,9 +1004,8 @@ int __ipv6_dev_mc_dec(struct inet6_dev *idev, const struct in6_addr *addr)
 {
 	struct ifmcaddr6 *ma, __rcu **map;
 
-	ASSERT_RTNL();
-
 	mutex_lock(&idev->mc_lock);
+
 	for (map = &idev->mc_list;
 	     (ma = mc_dereference(*map, idev));
 	     map = &ma->next) {
@@ -1037,13 +1036,12 @@ int ipv6_dev_mc_dec(struct net_device *dev, const struct in6_addr *addr)
 	struct inet6_dev *idev;
 	int err;
 
-	ASSERT_RTNL();
-
-	idev = __in6_dev_get(dev);
+	idev = in6_dev_get(dev);
 	if (!idev)
-		err = -ENODEV;
-	else
-		err = __ipv6_dev_mc_dec(idev, addr);
+		return -ENODEV;
+
+	err = __ipv6_dev_mc_dec(idev, addr);
+	in6_dev_put(idev);
 
 	return err;
 }