linux-kernel - Re: [RFC v3 8/9] kmsg: add predefined _PID, _TID,

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Message-ID: <CALCETrW2CgnS5pwS278ipLOSQi95UOT-osoSpshGwFmBf7TgRQ@mail.gmail.com>
Date:	Mon, 19 Oct 2015 10:45:54 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Paul Osmialowski <p.osmialowsk@...sung.com>
Cc:	Jonathan Corbet <corbet@....net>, Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Petr Mladek <pmladek@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	Kay Sievers <kay.sievers@...y.org>,
	Joe Perches <joe@...ches.com>, Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Marcin Niesluchowski <m.niesluchow@...sung.com>,
	Karol Lewandowski <k.lewandowsk@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [RFC v3 8/9] kmsg: add predefined _PID, _TID, _COMM keywords to
 kmsg* log dict

On Mon, Oct 19, 2015 at 5:58 AM, Paul Osmialowski
<p.osmialowsk@...sung.com> wrote:
> From: Marcin Niesluchowski <m.niesluchow@...sung.com>
>
> kmsg* devices write operation wrote no dict along with message
> Due to usage of kmsg devices in userspace dict has been added
> identifying pid, tid and comm of writing process.

Does this affect even the normal /dev/kmsg?

> -static int kmsg_sys_write(int minor, int level, const char *fmt, ...)
> +static size_t set_kmsg_dict(char *buf)
> +{
> +       size_t len;
> +
> +       len = sprintf(buf, "_PID=%d", task_tgid_nr(current)) + 1;
> +       len += sprintf(buf + len, "_TID=%d", task_pid_nr(current)) + 1;
> +       memcpy(buf + len, "_COMM=", 6);
> +       len += 6;
> +       get_task_comm(buf + len, current);
> +       while (buf[len] != '\0')
> +               len++;

len += strlen(buf); ?

Is it obvious for some reason that this doesn't overflow buf?

Why is task_pid_nr acceptable here?  Isn't this intended for use in namespaces?

--Andy
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