From: dsugar@tresys.com (David Sugar)
Date: Thu, 14 Sep 2017 13:45:19 +0000
Subject: [refpolicy] [PATCH 1/1] Add int_rlimit_inherit interface
In-Reply-To: <20170914082010.GB17010@julius.enp8s0.d30>
References: <1B50C12ACFF4CB42B90D2581155DF50205B5D882@Exchange10.columbia.tresys.com>
	<20170914080744.GA17010@julius.enp8s0.d30>,
	<20170914082010.GB17010@julius.enp8s0.d30>
Message-ID: <1B50C12ACFF4CB42B90D2581155DF50205B5ECA2@Exchange10.columbia.tresys.com>
To: refpolicy@oss.tresys.com
List-Id: refpolicy.oss.tresys.com


________________________________________
From: refpolicy-bounces@oss.tresys.com [refpolicy-bounces at oss.tresys.com] on behalf of Dominick Grift via refpolicy [refpolicy at oss.tresys.com]
Sent: Thursday, September 14, 2017 4:20 AM
To: refpolicy at oss.tresys.com
Subject: Re: [refpolicy] [PATCH 1/1] Add int_rlimit_inherit interface

On Thu, Sep 14, 2017 at 10:07:44AM +0200, Dominick Grift wrote:
> On Wed, Sep 13, 2017 at 08:34:15PM +0000, David Sugar via refpolicy wrote:
> > Create new interface init_rlimit_inherit to allow a process started by init to inherit resource limits.  systemd allows for setting of resource limits [1] but the default from SELinux is to not allow the inheritance of those limits as a service is started.  This interface allows that resource limit inheritance.
> >
> > The systemd .service options are LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=, LimitRSS=, LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=, LimitLOCKS=, LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=, LimitRTPRIO=, LimitRTTIME=
> >
> > [1] https://www.freedesktop.org/software/systemd/man/systemd.exec.html
>
> Have you tested this?
>
> I just tried this out and i do not seem to need this to get it to work:
>
> https://www.youtube.com/watch?v=f8nFGbMBG0s
>
> Instead systemd needs to be able to "setrlimit" (and probably getsched/setsched) on its children i suspect

I tested this in the use case that I am working with.  I am setting LimitMSGQUEUE=infinity in my .service file.  The service is starting a c++ binary which is creating a message queue (using mq_open) with a fairly large message queue size. 
I was getting failures to create the message queue (I'm pretty sure the error was EMFILE - I don't have the error message returned from mq_open handy any longer I can rebuild the policy and retest if you would like).  
Once I added this permission (and only this one change) the error went away.  

I did watch your video and I'm not sure what the difference is between the two cases.  I don't know if making it a bash script is somehow making a difference (I don't know why it would)?

I am also using the SELinuxContext= option to explicitly set the target domain.  I also don't think this would make a difference, but I wanted to mention it.

Dave Sugar
 
>
> >
> > Signed-off-by: Dave Sugar <dsugar@tresys.com>
> > ---
> >  policy/modules/system/init.if | 23 +++++++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> >
> > diff --git a/policy/modules/system/init.if b/policy/modules/system/init.if
> > index 09a20311..bf6e37bc 100644
> > --- a/policy/modules/system/init.if
> > +++ b/policy/modules/system/init.if
> > @@ -712,6 +712,29 @@ interface(`init_getpgid',`
> >
> >  ########################################
> >  ## <summary>
> > +## Allow process to inherit resource limits.
> > +## </summary>
> > +## <p>
> > +## This is applicable with systemd when using the
> > +## options to limit resources - see
> > +##  https://www.freedesktop.org/software/systemd/man/systemd.exec.html#LimitMSGQUEUE=
> > +## </p>
> > +## <param name="domain">
> > +## <summary>
> > +## Domain allowed access.
> > +## </summary>
> > +## </param>
> > +#
> > +interface(`init_rlimit_inherit',`
> > +   gen_require(`
> > +           type init_t;
> > +   ')
> > +
> > +   allow $1 init_t:process rlimitinh;
> > +')
> > +
> > +########################################
> > +## <summary>
> >  ## Send init a generic signal.
> >  ## </summary>
> >  ## <param name="domain">
> > --
> > 2.13.5
> > _______________________________________________
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>
> --
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> Dominick Grift



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Dominick Grift