On Tue, Nov 28, 2017 at 01:39:58PM -0800, Kees Cook wrote: > On Tue, Nov 28, 2017 at 1:16 PM, Luis R. Rodriguez <mcg...@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.
Ah, so system call implicated request_module() calls. > >> 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(). OK and since CAP_SYS_MODULE is much more restrictive one could argue, what's the point here? Luis
