ipv4: Check !in_dev earlier for ioctl(SIOCSIFADDR).

dev->ip_ptr could be NULL if we set an invalid MTU.

Even then, if we issue ioctl(SIOCSIFADDR) for a new IPv4 address,
devinet_ioctl() allocates struct in_ifaddr and fails later in
inet_set_ifa() because in_dev is NULL.

Let's move the check earlier.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20240809235406.50187-2-kuniyu@amazon.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/devinet.c

@@ -574,10 +574,6 @@ static int inet_set_ifa(struct net_device *dev, struct in_ifaddr *ifa)
 
 	ASSERT_RTNL();
 
-	if (!in_dev) {
-		inet_free_ifa(ifa);
-		return -ENOBUFS;
-	}
 	ipv4_devconf_setall(in_dev);
 	neigh_parms_data_state_setall(in_dev->arp_parms);
 	if (ifa->ifa_dev != in_dev) {
@@ -1184,6 +1180,8 @@ int devinet_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr)
 
 		if (!ifa) {
 			ret = -ENOBUFS;
+			if (!in_dev)
+				break;
 			ifa = inet_alloc_ifa();
 			if (!ifa)
 				break;