Re: [RFC v3 8/9] kmsg: add predefined _PID, _TID, _COMM keywords to kmsg* log dict

[Paul Osmialowski]

Hi Andy,

On Mon, 19 Oct 2015, Andy Lutomirski wrote:

> On Mon, Oct 19, 2015 at 5:58 AM, Paul Osmialowski
> <p.osmialowsk@xxxxxxxxxxx> wrote:
> > From: Marcin Niesluchowski <m.niesluchow@xxxxxxxxxxx>
> >
> > 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?

Yes.

> > -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?

KMSG_DICT_MAX_LEN sets architecture-intepentent max size.

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

task_tgid_nr - process id (pid as seen in userspace),
task_pid_nr - thread id

Thanks,
Paul
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