sctp: fix potential deadlock on &net->sctp.addr_wq_lock

sctp: fix potential deadlock on &net->sctp.addr_wq_lock

As &net->sctp.addr_wq_lock is also acquired by the timer
sctp_addr_wq_timeout_handler() in protocal.c, the same lock acquisition
at sctp_auto_asconf_init() seems should disable irq since it is called
from sctp_accept() under process context.

Possible deadlock scenario:
sctp_accept()
    -> sctp_sock_migrate()
    -> sctp_auto_asconf_init()
    -> spin_lock(&net->sctp.addr_wq_lock)
        <timer interrupt>
        -> sctp_addr_wq_timeout_handler()
        -> spin_lock_bh(&net->sctp.addr_wq_lock); (deadlock here)

This flaw was found using an experimental static analysis tool we are
developing for irq-related deadlock.

The tentative patch fix the potential deadlock by spin_lock_bh().

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Fixes: 34e5b0118685 ("sctp: delay auto_asconf init until binding the first addr")
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/20230627120340.19432-1-dg573847474@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>