lkml.org 
[lkml]   [2017]   [Nov]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 next 1/5] modules:capabilities: add request_module_cap()
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

\
 
 \ /
  Last update: 2017-11-28 22:17    [W:0.090 / U:2.412 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site