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From: Benjamin Gordon <bmgordon@google.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: linux-kernel@vger.kernel.org,
	John Stultz <john.stultz@linaro.org>,
	Kees Cook <keescook@chromium.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Oren Laadan <orenl@cellrox.com>,
	Ruchi Kandoi <kandoiruchi@google.com>,
	Rom Lemarchand <romlem@android.com>, Todd Kjos <tkjos@google.com>,
	Colin Cross <ccross@android.com>, Nick Kralevich <nnk@google.com>,
	Dmitry Shmidt <dimitrysh@google.com>,
	Elliott Hughes <enh@google.com>,
	Android Kernel Team <kernel-team@android.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] proc: use ns_capable instead of capable for timerslack_ns
Date: Tue, 30 Oct 2018 10:40:27 -0600	[thread overview]
Message-ID: <20181030164027.GA184838@google.com> (raw)
In-Reply-To: <87in1pn9d0.fsf@xmission.com>

On Thu, Oct 25, 2018 at 01:56:27PM -0500, Eric W. Biederman wrote:
> > Access to timerslack_ns is controlled by a process having CAP_SYS_NICE
> > in its effective capability set, but the current check looks in the root
> > namespace instead of the process' user namespace.  Since a process is
> > allowed to do other activities controlled by CAP_SYS_NICE inside a
> > namespace, it should also be able to adjust timerslack_ns.
> 
> The goal seems legitimate.  However the permission checks look wrong.
> 
> In particular the choice of user namespace should be
> "p->cred->user_ns".  This will limit this to tasks that have
> CAP_SYS_NICE in the same namespace as the task that is being modified.
> 
> Testing file->f_cred->user_ns it is testing whoever opened the file and
> that could be anyone.

Thanks, that seems like the right answer here.  I'll send a v2 to fix
it.

Thanks,
Benjamin

      reply	other threads:[~2018-10-30 16:40 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-17 22:47 [PATCH] proc: use ns_capable instead of capable for timerslack_ns bmgordon
2018-10-25 17:09 ` Benjamin Gordon
2018-10-25 17:20 ` John Stultz
2018-10-25 18:56 ` Eric W. Biederman
2018-10-30 16:40   ` Benjamin Gordon [this message]

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