netdev - Re: [PATCH net] sctp: add a refcnt in sctp_stream

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Message-ID: <Y+5KRT0FYiI3t25n@t14s.localdomain>
Date:   Thu, 16 Feb 2023 07:22:45 -0800
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net, kuba@...nel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Neil Horman <nhorman@...driver.com>,
        Zhengchao Shao <shaozhengchao@...wei.com>
Subject: Re: [PATCH net] sctp: add a refcnt in sctp_stream_priorities to
 avoid a nested loop

On Wed, Feb 15, 2023 at 03:04:44PM -0500, Xin Long wrote:
> With this refcnt added in sctp_stream_priorities, we don't need to
> traverse all streams to check if the prio is used by other streams
> when freeing one stream's prio in sctp_sched_prio_free_sid(). This
> can avoid a nested loop (up to 65535 * 65535), which may cause a
> stuck as Ying reported:
> 
>     watchdog: BUG: soft lockup - CPU#23 stuck for 26s! [ksoftirqd/23:136]
>     Call Trace:
>      <TASK>
>      sctp_sched_prio_free_sid+0xab/0x100 [sctp]
>      sctp_stream_free_ext+0x64/0xa0 [sctp]
>      sctp_stream_free+0x31/0x50 [sctp]
>      sctp_association_free+0xa5/0x200 [sctp]
> 
> Note that it doesn't need to use refcount_t type for this counter,
> as its accessing is always protected under the sock lock.
> 
> Fixes: 9ed7bfc79542 ("sctp: fix memory leak in sctp_stream_outq_migrate()")
> Reported-by: Ying Xu <yinxu@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>