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Date:   Thu, 23 Feb 2023 19:02:39 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Xin Long <lucien.xin@gmail.com>
Cc:     network dev <netdev@vger.kernel.org>, linux-sctp@vger.kernel.org,
        davem@davemloft.net, Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
        Neil Horman <nhorman@tuxdriver.com>,
        Zhengchao Shao <shaozhengchao@huawei.com>
Subject: Re: [PATCHv2 net] sctp: add a refcnt in sctp_stream_priorities to
 avoid a nested loop
Message-ID: <20230223190239.34932117@kernel.org>
In-Reply-To: <825eb0c905cb864991eba335f4a2b780e543f06b.1677085641.git.lucien.xin@gmail.com>
References: <825eb0c905cb864991eba335f4a2b780e543f06b.1677085641.git.lucien.xin@gmail.com>
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On Wed, 22 Feb 2023 12:07:21 -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.
> 
> v1->v2:
>  - add a check in sctp_sched_prio_set to avoid the possible prio_head
>    refcnt overflow.
> 
> Fixes: 9ed7bfc79542 ("sctp: fix memory leak in sctp_stream_outq_migrate()")
> Reported-by: Ying Xu <yinxu@redhat.com>
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Applied, thanks!