sctp_packet_transmit NULL pointer dereference kernel panic

Issue

• NULL pointer dereference kernel panic in sctp_packet_transmit with call trace similar to:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
IP: [<ffffffffa0096b32>] sctp_packet_transmit+0x502/0x570 [sctp]
CPU: 14 PID: 0 Comm: swapper/14 Tainted: GF          O--------------   3.10.0-229.el7.x86_64 #1
RIP: 0010:[<ffffffffa0096b32>]  [<ffffffffa0096b32>] sctp_packet_transmit+0x502/0x570 [sctp]
Call Trace:
 [<ffffffffa00961a0>] ? __sctp_packet_append_chunk+0xc0/0x1b0 [sctp]
 [<ffffffffa009647b>] ? sctp_packet_append_chunk+0xfb/0x260 [sctp]
 [<ffffffffa00770e2>] ? sctp_sf_pdiscard+0x42/0x60 [sctp]
 [<ffffffffa007e64b>] sctp_cmd_interpreter.isra.25+0xcbb/0x1330 [sctp]
 [<ffffffffa007a004>] ? sctp_sf_do_5_1B_init+0x314/0x330 [sctp]
 [<ffffffffa007a004>] ? sctp_sf_do_5_1B_init+0x314/0x330 [sctp]
 [<ffffffffa007d43f>] sctp_do_sm+0xaf/0x1b0 [sctp]
 [<ffffffffa00803b4>] sctp_endpoint_bh_rcv+0x124/0x260 [sctp]
 [<ffffffffa00893ac>] sctp_inq_push+0x4c/0x70 [sctp]
 [<ffffffffa00976e4>] sctp_rcv+0x9b4/0xa40 [sctp]
 [<ffffffff81112948>] ? __call_rcu_nocb_enqueue+0xa8/0xc0
 [<ffffffff8111386d>] ? call_rcu_sched+0x1d/0x20
 [<ffffffff815b4af9>] ? ip_route_input_noref+0x6f9/0xbd0
 [<ffffffff810b4fd6>] ? update_group_power+0x136/0x210
 [<ffffffff815b6a64>] ip_local_deliver_finish+0xb4/0x1f0
 [<ffffffff815b6d38>] ip_local_deliver+0x48/0x80
 [<ffffffff815b66dd>] ip_rcv_finish+0x7d/0x350
 [<ffffffff815b6fa4>] ip_rcv+0x234/0x380