Re: [PATCH RFC 3/5] printk: modify printk interface for syslog_namespace

Quoting Libo Chen (chenlibo.3-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org):

From: Libo Chen <redacted>

On 2012-11-25 12:28, Serge E. Hallyn wrote:

quoted

Quoting Libo Chen (chenlibo.3-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org):

quoted

On 2012/11/22 1:49, Serge E. Hallyn wrote:

quoted

I notice that you haven't made any changes to the struct cont.  I
suspect this means that to-be-continued msgs from one ns can be
erroneously mixed with another ns.

Yes, I confirmed this problem. There will be erroneously mixed with another ns.
Thank you very much.

quoted

You said you don't mind putting the syslogns into the userns.  If
there's no reason not to do that, then we should do so as it will
remove a bunch of code (plus the use of a new CLONE flag) from your
patch, and the new syslog(NEW_NS) command from mine.

I agree with you, both are removable.

quoted

Now IMO the ideal place for syslog_ns would be in the devices ns,
but that does not yet exist, and may never.  The bonus to that would
be that the consoles sort of belong there.  I avoid this by not
having consoles in child syslog namespaces.  You put the console in
the ns.  I haven't looked closely enough to see if what you do is
ok (will do so soon).

WOuld you mind looking through my patch to see if it suffices for
your needs?  Where it does not, patches would be greatly appreciated
if simple enough.

follow your patch, I can see inject message by "dmesg call" in container, is right?

If I understand you right, yes.

quoted

I am worry that I debug  or see messages from serial ports console in some embedded system,
since console belongs to init_syslog,  so the message in container can`t be printed. 

Sorry, I don't understand which way you're going with that.  Could you
rephrase?  You want to prevent console messages from going to a
container?  (That should definately not happen)  Or something else?

I reviewed your patch, and found that console could only print messages
belonging to init_syslog.

So the message belongs to container syslog can not be printed from console,
but only "dmesg call" in user space.  Is that right?

For example, the messages can not be outputed automatically from serial port
as a kind of consoles on some embedded system.

Oh, I see.  I basically thought this was a feature, not a problem :)  But
that wasn't meant to be a core part of my patchset, rather I wasn't quite
sure how best to handle it, so I put it off for later.  My main concern is
that if consoles in containers are supported, this must NOT lead to
kernel module loading from the container.

And I am not sure if there are no other problems.

Ok, I will write a new patch which would (a) try to address the consoles,
(b) move the syslogns into the user_ns (making it no longer a syslog_ns),
and (c) adding some users of ns_printk (borrowing the ones from your
set for starters).

thanks,
-serge