ipv4: Set ifa->ifa_dev in inet_alloc_ifa().

When a new IPv4 address is assigned via ioctl(SIOCSIFADDR),
inet_set_ifa() sets ifa->ifa_dev if it's different from in_dev
passed as an argument.

In this case, ifa is always a newly allocated object, and
ifa->ifa_dev is NULL.

inet_set_ifa() can be called for an existing reused ifa, then,
this check is always false.

Let's set ifa_dev in inet_alloc_ifa() and remove the check
in inet_set_ifa().

Now, inet_alloc_ifa() is symmetric with inet_rcu_free_ifa().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20240809235406.50187-3-kuniyu@amazon.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/devinet.c

@@ -216,9 +216,18 @@ static void devinet_sysctl_unregister(struct in_device *idev)
 
 /* Locks all the inet devices. */
 
-static struct in_ifaddr *inet_alloc_ifa(void)
+static struct in_ifaddr *inet_alloc_ifa(struct in_device *in_dev)
 {
-	return kzalloc(sizeof(struct in_ifaddr), GFP_KERNEL_ACCOUNT);
+	struct in_ifaddr *ifa;
+
+	ifa = kzalloc(sizeof(*ifa), GFP_KERNEL_ACCOUNT);
+	if (!ifa)
+		return NULL;
+
+	in_dev_hold(in_dev);
+	ifa->ifa_dev = in_dev;
+
+	return ifa;
 }
 
 static void inet_rcu_free_ifa(struct rcu_head *head)
@@ -576,11 +585,7 @@ static int inet_set_ifa(struct net_device *dev, struct in_ifaddr *ifa)
 
 	ipv4_devconf_setall(in_dev);
 	neigh_parms_data_state_setall(in_dev->arp_parms);
-	if (ifa->ifa_dev != in_dev) {
-		WARN_ON(ifa->ifa_dev);
-		in_dev_hold(in_dev);
-		ifa->ifa_dev = in_dev;
-	}
+
 	if (ipv4_is_loopback(ifa->ifa_local))
 		ifa->ifa_scope = RT_SCOPE_HOST;
 	return inet_insert_ifa(ifa);
@@ -871,7 +876,7 @@ static struct in_ifaddr *rtm_to_ifaddr(struct net *net, struct nlmsghdr *nlh,
 	if (!in_dev)
 		goto errout;
 
-	ifa = inet_alloc_ifa();
+	ifa = inet_alloc_ifa(in_dev);
 	if (!ifa)
 		/*
 		 * A potential indev allocation can be left alive, it stays
@@ -881,7 +886,6 @@ static struct in_ifaddr *rtm_to_ifaddr(struct net *net, struct nlmsghdr *nlh,
 
 	ipv4_devconf_setall(in_dev);
 	neigh_parms_data_state_setall(in_dev->arp_parms);
-	in_dev_hold(in_dev);
 
 	if (!tb[IFA_ADDRESS])
 		tb[IFA_ADDRESS] = tb[IFA_LOCAL];
@@ -892,8 +896,6 @@ static struct in_ifaddr *rtm_to_ifaddr(struct net *net, struct nlmsghdr *nlh,
 	ifa->ifa_flags = tb[IFA_FLAGS] ? nla_get_u32(tb[IFA_FLAGS]) :
 					 ifm->ifa_flags;
 	ifa->ifa_scope = ifm->ifa_scope;
-	ifa->ifa_dev = in_dev;
-
 	ifa->ifa_local = nla_get_in_addr(tb[IFA_LOCAL]);
 	ifa->ifa_address = nla_get_in_addr(tb[IFA_ADDRESS]);
 
@@ -1182,7 +1184,7 @@ int devinet_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr)
 			ret = -ENOBUFS;
 			if (!in_dev)
 				break;
-			ifa = inet_alloc_ifa();
+			ifa = inet_alloc_ifa(in_dev);
 			if (!ifa)
 				break;
 			INIT_HLIST_NODE(&ifa->hash);
@@ -1584,7 +1586,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 		if (!inetdev_valid_mtu(dev->mtu))
 			break;
 		if (dev->flags & IFF_LOOPBACK) {
-			struct in_ifaddr *ifa = inet_alloc_ifa();
+			struct in_ifaddr *ifa = inet_alloc_ifa(in_dev);
 
 			if (ifa) {
 				INIT_HLIST_NODE(&ifa->hash);
@@ -1592,8 +1594,6 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 				  ifa->ifa_address = htonl(INADDR_LOOPBACK);
 				ifa->ifa_prefixlen = 8;
 				ifa->ifa_mask = inet_make_mask(8);
-				in_dev_hold(in_dev);
-				ifa->ifa_dev = in_dev;
 				ifa->ifa_scope = RT_SCOPE_HOST;
 				memcpy(ifa->ifa_label, dev->name, IFNAMSIZ);
 				set_ifa_lifetime(ifa, INFINITY_LIFE_TIME,