From: Xin Long <lucien.xin@xxxxxxxxx>
Date: Fri, 21 Aug 2020 14:59:38 +0800
> With disabling bh in the whole sctp_get_port_local(), when
> snum == 0 and too many ports have been used, the do-while
> loop will take the cpu for a long time and cause cpu stuck:
>
> [ ] watchdog: BUG: soft lockup - CPU#11 stuck for 22s!
> [ ] RIP: 0010:native_queued_spin_lock_slowpath+0x4de/0x940
> [ ] Call Trace:
> [ ] _raw_spin_lock+0xc1/0xd0
> [ ] sctp_get_port_local+0x527/0x650 [sctp]
> [ ] sctp_do_bind+0x208/0x5e0 [sctp]
> [ ] sctp_autobind+0x165/0x1e0 [sctp]
> [ ] sctp_connect_new_asoc+0x355/0x480 [sctp]
> [ ] __sctp_connect+0x360/0xb10 [sctp]
>
> There's no need to disable bh in the whole function of
> sctp_get_port_local. So fix this cpu stuck by removing
> local_bh_disable() called at the beginning, and using
> spin_lock_bh() instead.
>
> The same thing was actually done for inet_csk_get_port() in
> Commit ea8add2b1903 ("tcp/dccp: better use of ephemeral
> ports in bind()").
>
> Thanks to Marcelo for pointing the buggy code out.
>
> v1->v2:
> - use cond_resched() to yield cpu to other tasks if needed,
> as Eric noticed.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: Ying Xu <yinxu@xxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Applied and queued up for -stable, thank you.
