linux-kernel - Re: [PATCH net] sctp: fix sleep in atomic context bug in timer handlers

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Message-ID: <Yt1Fbv9t/BBeYe1Z@t14s.localdomain>
Date:   Sun, 24 Jul 2022 10:13:18 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Duoming Zhou <duoming@....edu.cn>
Cc:     linux-sctp@...r.kernel.org, vyasevich@...il.com,
        nhorman@...driver.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] sctp: fix sleep in atomic context bug in timer
 handlers

Hi,

On Sat, Jul 23, 2022 at 09:58:09AM +0800, Duoming Zhou wrote:
> There are sleep in atomic context bugs in timer handlers of sctp
> such as sctp_generate_t3_rtx_event(), sctp_generate_probe_event(),
> sctp_generate_t1_init_event(), sctp_generate_timeout_event(),
> sctp_generate_t3_rtx_event() and so on.
> 
> The root cause is sctp_sched_prio_init_sid() with GFP_KERNEL parameter
> that may sleep could be called by different timer handlers which is in
> interrupt context.
> 
> One of the call paths that could trigger bug is shown below:
> 
>       (interrupt context)
> sctp_generate_probe_event
>   sctp_do_sm
>     sctp_side_effects
>       sctp_cmd_interpreter
>         sctp_outq_teardown
>           sctp_outq_init

This sequence is odd but it is used when handling dup cookies. It
tears down whatever was in there and re-inits it. With that,

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

>             sctp_sched_set_sched
>               n->init_sid(..,GFP_KERNEL)
>                 sctp_sched_prio_init_sid //may sleep