netns: fix net_alloc_generic()
netns: fix net_alloc_generic()

When a new net namespace is created, we should attach to it a "struct
net_generic" with enough slots (even empty), or we can hit the following
BUG_ON() :

[  200.752016] kernel BUG at include/net/netns/generic.h:40!
...
[  200.752016]  [<ffffffff825c3cea>] ? get_cfcnfg+0x3a/0x180
[  200.752016]  [<ffffffff821cf0b0>] ? lockdep_rtnl_is_held+0x10/0x20
[  200.752016]  [<ffffffff825c41be>] caif_device_notify+0x2e/0x530
[  200.752016]  [<ffffffff810d61b7>] notifier_call_chain+0x67/0x110
[  200.752016]  [<ffffffff810d67c1>] raw_notifier_call_chain+0x11/0x20
[  200.752016]  [<ffffffff821bae82>] call_netdevice_notifiers+0x32/0x60
[  200.752016]  [<ffffffff821c2b26>] register_netdevice+0x196/0x300
[  200.752016]  [<ffffffff821c2ca9>] register_netdev+0x19/0x30
[  200.752016]  [<ffffffff81c1c67a>] loopback_net_init+0x4a/0xa0
[  200.752016]  [<ffffffff821b5e62>] ops_init+0x42/0x180
[  200.752016]  [<ffffffff821b600b>] setup_net+0x6b/0x100
[  200.752016]  [<ffffffff821b6466>] copy_net_ns+0x86/0x110
[  200.752016]  [<ffffffff810d5789>] create_new_namespaces+0xd9/0x190

net_alloc_generic() should take into account the maximum index into the
ptr array, as a subsystem might use net_generic() anytime.

This also reduces number of reallocations in net_assign_generic()

Reported-by: Sasha Levin <611d453c03d02ce713e72b62ff6a901ea7e9cd77@gmail.com>
Tested-by: Sasha Levin <611d453c03d02ce713e72b62ff6a901ea7e9cd77@gmail.com>
Signed-off-by: Eric Dumazet <a0baddf32b28d2f9429941ed4af2fe636e210591@gmail.com>
Cc: Sjur Brændeland <90c9f68dc7b20ac89683f2c4f55e4a05e8dbf9ad@stericsson.com>
Cc: Eric W. Biederman <8a741aa8cbd77ebc4a56ddb528ce9fd15d42f034@xmission.com>
Cc: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@openvz.org>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas