net/smc: use smc_lgr_list.lock to protect smc_lgr_list.list iterate in smcr_port_add
While doing smcr_port_add, there maybe linkgroup add into or delete from smc_lgr_list.list at the same time, which may result kernel crash. So, use smc_lgr_list.lock to protect smc_lgr_list.list iterate in smcr_port_add. The crash calltrace show below: BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 PID: 559726 Comm: kworker/0:92 Kdump: loaded Tainted: G Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 449e491 04/01/2014 Workqueue: events smc_ib_port_event_work [smc] RIP: 0010:smcr_port_add+0xa6/0xf0 [smc] RSP: 0000:ffffa5a2c8f67de0 EFLAGS: 00010297 RAX: 0000000000000001 RBX: ffff9935e0650000 RCX: 0000000000000000 RDX: 0000000000000010 RSI: ffff9935e0654290 RDI: ffff9935c8560000 RBP: 0000000000000000 R08: 0000000000000000 R09: ffff9934c0401918 R10: 0000000000000000 R11: ffffffffb4a5c278 R12: ffff99364029aae4 R13: ffff99364029aa00 R14: 00000000ffffffed R15: ffff99364029ab08 FS: 0000000000000000(0000) GS:ffff994380600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000f06a10003 CR4: 0000000002770ef0 PKRU: 55555554 Call Trace: smc_ib_port_event_work+0x18f/0x380 [smc] process_one_work+0x19b/0x340 worker_thread+0x30/0x370 ? process_one_work+0x340/0x340 kthread+0x114/0x130 ? __kthread_cancel_work+0x50/0x50 ret_from_fork+0x1f/0x30 Fixes: 1f90a05d ("net/smc: add smcr_port_add() and smcr_link_up() processing") Signed-off-by:Guangguan Wang <guangguan.wang@linux.alibaba.com> Signed-off-by: