linux-kernel - Re: [PATCH v4 2/5] connector: use __get_task_comm in proc_comm

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Message-ID: <CALOAHbDb7OicA1m8CTCX3RS9h5N=_xS-Jiq+88Nn4A1Vk6TWrw@mail.gmail.com>
Date:   Thu, 14 Oct 2021 10:42:42 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        qiang.zhang@...driver.com, robdclark@...omium.org,
        christian@...uner.io, Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Benjamin Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        David Miller <davem@...emloft.net>, kuba@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Vladimir Zapolskiy <vzapolskiy@...il.com>,
        David Howells <dhowells@...hat.com>
Subject: Re: [PATCH v4 2/5] connector: use __get_task_comm in proc_comm_connector

On Thu, Oct 14, 2021 at 10:24 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Thu, 14 Oct 2021 09:48:09 +0800
> Yafang Shao <laoar.shao@...il.com> wrote:
>
> > > __get_task_comm() uses strncpy() which my understanding is, does not add
> > > the nul terminating byte when truncating. Which changes the functionality
> > > here. As all task comms have a terminating byte, the old method would copy
> > > that and include it. This won't add the terminating byte if the buffer is
> > > smaller than the comm, and that might cause issues.
> > >
> >
> > Right, that is a problem.
> > It seems that we should add a new helper get_task_comm_may_truncated().
>
> Or simply change __get_task_comm() to:
>
> char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
> {
>         task_lock(tsk);
>         strncpy(buf, tsk->comm, buf_size);
>         /* The copied value is always nul terminated */
>         buf[buf_size - 1] = '\0';
>         task_unlock(tsk);
>         return buf;
> }
>

That is better! Thanks for the suggestion.

> But that should probably be a separate patch.
>

Sure.

-- 
Thanks
Yafang