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. >> 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
