On Tue, 2023-06-27 at 12:03 +0000, Chengfeng Ye wrote:

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().

Patch LGTM.

Please note that the above suggests a possible net-next follow-
up/cleanup, replacing the spin_lock_bh() in
sctp_addr_wq_timeout_handler() with a simple/faster spin_lock() - since
sctp_addr_wq_timeout_handler() runs with BH disabled. Anyhow net-next
is closed now, it will have to wait a bit ;)

Cheers,

Paolo