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From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Djalal Harouni <tixxdz@gmail.com>,
	Andy Lutomirski <luto@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	James Morris <james.l.morris@oracle.com>,
	Ben Hutchings <ben.hutchings@codethink.co.uk>,
	Solar Designer <solar@openwall.com>,
	Serge Hallyn <serge@hallyn.com>, Jessica Yu <jeyu@kernel.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	kernel-hardening@lists.openwall.com,
	Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Network Development <netdev@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v5 next 1/5] modules:capabilities: add request_module_cap()
Date: Tue, 28 Nov 2017 22:16:59 +0100	[thread overview]
Message-ID: <20171128211659.GP729@wotan.suse.de> (raw)
In-Reply-To: <CAGXu5jKgHWNE4NH_xqcM084-BNBPy+HmEVPbTA+w_=K3S6gC=w@mail.gmail.com>

On Tue, Nov 28, 2017 at 12:11:34PM -0800, Kees Cook wrote:
> On Tue, Nov 28, 2017 at 11:14 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> > kmod is just a helper to poke userpsace to load a module, that's it.
> >
> > The old init_module() and newer finit_module() do the real handy work or
> > module loading, and both currently only use may_init_module():
> >
> > static int may_init_module(void)
> > {
> >         if (!capable(CAP_SYS_MODULE) || modules_disabled)
> >                 return -EPERM;
> >
> >         return 0;
> > }
> >
> > This begs the question:
> >
> >   o If userspace just tries to just use raw finit_module() do we want similar
> >     checks?
> >
> > Otherwise, correct me if I'm wrong this all seems pointless.
> 
> Hm? That's direct-loading, not auto-loading. This series is only about
> auto-loading.

And *all* auto-loading uses aliases? What's the difference between auto-loading
and direct-loading?

> We already have a global sysctl for blocking direct-loading (modules_disabled).

My point was that even if you have a CAP_NET_ADMIN check on request_module(),
finit_module() will not check for it, so a crafty userspace could still try
to just finit_module() directly, and completely then bypass the CAP_NET_ADMIN
check.

So unless I'm missing something, I see no point in adding extra checks for
request_module() but nothing for the respective load_module().

  Luis

  reply	other threads:[~2017-11-28 21:17 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-27 17:18 [PATCH v5 next 0/5] Improve Module autoloading infrastructure Djalal Harouni
2017-11-27 17:18 ` [PATCH v5 next 1/5] modules:capabilities: add request_module_cap() Djalal Harouni
2017-11-27 18:48   ` Randy Dunlap
2017-11-27 21:35     ` Djalal Harouni
2017-11-28 19:14   ` Luis R. Rodriguez
2017-11-28 20:11     ` Kees Cook
2017-11-28 21:16       ` Luis R. Rodriguez [this message]
2017-11-28 21:33         ` Djalal Harouni
2017-11-28 22:18           ` Luis R. Rodriguez
2017-11-28 22:52             ` Djalal Harouni
2017-11-28 21:39         ` Kees Cook
2017-11-28 22:12           ` Luis R. Rodriguez
2017-11-28 22:18             ` Kees Cook
2017-11-28 22:48               ` Luis R. Rodriguez
2017-11-29  7:49                 ` Michal Kubecek
2017-11-29 13:46           ` Alan Cox
2017-11-29 14:50             ` David Miller
2017-11-29 15:54               ` Theodore Ts'o
2017-11-29 15:58                 ` David Miller
2017-11-29 16:29                   ` Theodore Ts'o
2017-11-29 22:45                   ` Linus Torvalds
2017-11-30  0:06                     ` Kees Cook
2017-11-29 17:28                 ` Serge E. Hallyn
2017-11-30  0:35                   ` Theodore Ts'o
2017-11-30 17:17                     ` Serge E. Hallyn
2017-11-28 20:18     ` Djalal Harouni
2017-11-27 17:18 ` [PATCH v5 next 2/5] modules:capabilities: add cap_kernel_module_request() permission check Djalal Harouni
2017-11-30  2:05   ` Luis R. Rodriguez
2017-11-27 17:18 ` [PATCH v5 next 3/5] modules:capabilities: automatic module loading restriction Djalal Harouni
2017-11-30  1:23   ` Luis R. Rodriguez
2017-11-30 12:22     ` Djalal Harouni
2017-11-27 17:18 ` [PATCH v5 next 4/5] modules:capabilities: add a per-task modules auto-load mode Djalal Harouni
2017-11-27 17:18 ` [PATCH v5 next 5/5] net: modules: use request_module_cap() to load 'netdev-%s' modules Djalal Harouni
2017-11-27 18:44   ` Linus Torvalds
2017-11-27 21:41     ` Djalal Harouni
2017-11-27 22:04       ` Linus Torvalds
2017-11-27 22:59         ` Kees Cook
2017-11-27 23:14           ` Linus Torvalds
2017-11-27 23:19             ` Kees Cook
2017-11-27 23:35               ` Linus Torvalds
2017-11-28  1:23             ` Kees Cook
2017-11-27 18:41 ` [PATCH v5 next 0/5] Improve Module autoloading infrastructure Linus Torvalds
2017-11-27 19:02   ` Linus Torvalds
2017-11-27 19:12     ` Linus Torvalds
2017-11-27 21:31       ` Djalal Harouni
2017-11-27 19:14   ` David Miller
2017-11-27 22:31     ` James Morris
2017-11-27 23:04       ` Kees Cook
2017-11-27 23:44         ` James Morris

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