Re: [Patch 5/8] mqueue: revert bump up DFLT_*MAX

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting Doug Ledford (dledford@redhat.com):
> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> 
> Mqueue limitation is slightly naieve parameter likes other ipcs
> because unprivileged user can consume kernel memory by using ipcs.
> 
> Thus, too aggressive raise bring us security issue. Example,
> current setting allow evil unprivileged user use 256GB (= 256
> * 1024 * 1024*1024) and it's enough large to system will belome
> unresponsive. Don't do that.
> 
> Instead, every admin should adjust the knobs for their own systems.

Would you be terribly averse to having a higher limit in init_ipc_ns,
and the lower values by default in all child namespaces?

Sorry it sounds from the intro like you've already had quite a bit of
discussion on this...

Of course I realize the values can just be raised by distro boot
scripts...

> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Acked-by: Doug Ledford <dledford@redhat.com>
> Acked-by: Joe Korty <joe.korty@ccur.com>
> Cc: Amerigo Wang <amwang@redhat.com>
> Cc: Serge E. Hallyn <serue@us.ibm.com>

Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>

> Cc: Jiri Slaby <jslaby@suse.cz>
> ---
>  include/linux/ipc_namespace.h |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
> index 6e1dd08..2488535 100644
> --- a/include/linux/ipc_namespace.h
> +++ b/include/linux/ipc_namespace.h
> @@ -118,12 +118,12 @@ extern int mq_init_ns(struct ipc_namespace *ns);
>  #define DFLT_QUEUESMAX		      256
>  #define HARD_QUEUESMAX		     1024
>  #define MIN_MSGMAX			1
> -#define DFLT_MSG		       64U
> -#define DFLT_MSGMAX		     1024
> +#define DFLT_MSG		       10U
> +#define DFLT_MSGMAX		       10
>  #define HARD_MSGMAX		    65536
>  #define MIN_MSGSIZEMAX		      128
>  #define DFLT_MSGSIZE		     8192U
> -#define DFLT_MSGSIZEMAX	       (1024*1024)
> +#define DFLT_MSGSIZEMAX		     8192
>  #define HARD_MSGSIZEMAX	    (16*1024*1024)
>  #else
>  static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
> -- 
> 1.7.7.6
> 
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