lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 7 Dec 2012 18:30:53 +0400
From:	Glauber Costa <>
To:	Serge Hallyn <>
CC:	Andrew Morton <>,
	Rui Xiang <>, <>,
	"Eric W. Biederman" <>
Subject: Re: [PATCH RFC 0/5] Containerize syslog

On 12/07/2012 06:23 PM, Serge Hallyn wrote:
> Quoting Andrew Morton (
>> On Mon, 19 Nov 2012 01:51:09 -0800 (Eric W. Biederman) wrote:
>>> Are there any kernel print statements besides networking stack printks
>>> that we want to move to show up in a new "kernel log" namespace?
>> That's a good question, and afaict it remains unanswered.
> There are some other (not *terribly* compelling) cases.  For instance
> selinux hooks, if you say mount an fs without xattr support or with
> unsupported options, will printk a warning.  Things like stat.c and
> capabilities and syslog print out warnings when userspace uses a
> deprecated somethingorother - old stat syscall or sys_syslog without
> CAP_SYSLOG.  That should go to the container.  Filesystems may give
> warnings (bad mount options for tmpfs, bad uid owner for many of them,
> etc) which belong in the container.  Obviously some belong on the host -
> if they show a corrupt superblock which may indicate an attempt by the
> container to crash the kernel.
>> As so often happens, this patchset's changelogs forgot to describe the
>> reason for the existence of this patchset.  Via a bit of lwn reading
> Not as a separate justification admittedly, but the description was
> meant to explain it:  right now /dev/kmsg and sys_syslog are not safe
> and useful in a container;  syslog messages from host and containers
> can be confusingly intermixed;  and helpful printks are not seen in
> the container.
>> and my awesome telepathic skills, I divine that something in networking
>> is using syslog for kernel->userspace communications.
>> wtf?
> Well, syslog is the kernel->userspace channel of last resort.
>> Wouldn't it be better to just stop doing that, and to implement a
>> respectable and reliable kernel->userspace messaging scheme?
> Convenience functions on top of netlink?
>> And leave syslog alone - it's a crude low-level thing for random
>> unexpected things which operators might want to know about.
> That sentence is a result of not calling a container admin an operator.
> I can't argue it because I'm not sure whether to agree with that
> classification.

I keep asking myself if it isn't the case of forwarding to a container
all messages printed in process context. That will obviously exclude all
messages resulting from kthreads - that will always be in the initial
namespace anyway, interrupts, etc. There is no harm, for instance, in
delivering the same message twice: one to the container, and the other
to the host system.

Isn't it natural that if the kernel printed something on behalf of a
process, whoever is the admin of the machine that process lives on
should see what it is about?

To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists