Messages in this thread | | | From | Kees Cook <> | Date | Tue, 28 Nov 2017 13:39:58 -0800 | Subject | Re: [PATCH v5 next 1/5] modules:capabilities: add request_module_cap() |
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On Tue, Nov 28, 2017 at 1:16 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote: > And *all* auto-loading uses aliases? What's the difference between auto-loading > and direct-loading?
The difference is the process privileges. Unprivilged autoloading (e.g. int n_hdlc = N_HDLC; ioctl(fd, TIOCSETD, &n_hdlc)), triggers a privileged call to finit_module() under CAP_SYS_MODULE.
>> 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.
You need CAP_SYS_MODULE to run finit_module().
-Kees
-- Kees Cook Pixel Security
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