net: ipv4: fix one memleak in __inet_del_ifa()

In the Linux kernel, the following vulnerability has been resolved:

net: ipv4: fix one memleak in __inet_del_ifa()

I got the below warning when do fuzzing test:

unregister_netdevice: waiting for bond0 to become free. Usage count = 2

It can be repoduced via:

ip link add bond0 type bond

sysctl -w net.ipv4.conf.bond0.promote_secondaries=1

ip addr add 4.117.174.103/0 scope 0x40 dev bond0

ip addr add 192.168.100.111/255.255.255.254 scope 0 dev bond0

ip addr add 0.0.0.4/0 scope 0x40 secondary dev bond0

ip addr del 4.117.174.103/0 scope 0x40 dev bond0

ip link delete bond0 type bond

In this reproduction test case, an incorrect 'last_prim' is found in

__inet_del_ifa(), as a result, the secondary address(0.0.0.4/0 scope 0x40)

is lost. The memory of the secondary address is leaked and the reference of

in_device and net_device is leaked.

Fix this problem:

Look for 'last_prim' starting at location of the deleted IP and inserting

the promoted IP into the location of 'last_prim'.