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Date:   Wed, 13 Oct 2021 10:19:21 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Yafang Shao <laoar.shao@gmail.com>
Cc:     keescook@chromium.org, peterz@infradead.org, pmladek@suse.com,
        viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
        valentin.schneider@arm.com, mathieu.desnoyers@efficios.com,
        qiang.zhang@windriver.com, robdclark@chromium.org,
        christian@brauner.io, dietmar.eggemann@arm.com, mingo@redhat.com,
        juri.lelli@redhat.com, vincent.guittot@linaro.org,
        bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
        davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org,
        Vladimir Zapolskiy <vzapolskiy@gmail.com>,
        David Howells <dhowells@redhat.com>
Subject: Re: [PATCH v4 2/5] connector: use __get_task_comm in
 proc_comm_connector
Message-ID: <20211013101921.0843aaf0@gandalf.local.home>
In-Reply-To: <20211013102346.179642-3-laoar.shao@gmail.com>
References: <20211013102346.179642-1-laoar.shao@gmail.com>
        <20211013102346.179642-3-laoar.shao@gmail.com>
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On Wed, 13 Oct 2021 10:23:43 +0000
Yafang Shao <laoar.shao@gmail.com> wrote:

> --- a/drivers/connector/cn_proc.c
> +++ b/drivers/connector/cn_proc.c
> @@ -230,7 +230,10 @@ void proc_comm_connector(struct task_struct *task)
>  	ev->what = PROC_EVENT_COMM;
>  	ev->event_data.comm.process_pid  = task->pid;
>  	ev->event_data.comm.process_tgid = task->tgid;
> -	get_task_comm(ev->event_data.comm.comm, task);
> +
> +	/* This may get truncated. */
> +	__get_task_comm(ev->event_data.comm.comm,
> +			sizeof(ev->event_data.comm.comm), task);
>  
>  	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
>  	msg->ack = 0; /* not used */

__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.

-- Steve