On Fri, Jul 25, 2014 at 7:30 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > [new thread because this sort of combines two threads] > > There is recent interest in having a way to turn generally-available > kernel features off. Maybe we should add a good one so we can stop > bikeshedding and avoid proliferating dumb interfaces. > > Things that might want to be turn-off-able include: > - getrandom with GRND_RANDOM [from the getrandom threads] > - Any lookup of a non-self pid [from the capsicum thread] > - Any lookup of a pid outside the caller thread group [capsicum] > - Various architectural things (personal wishlist), e.g.: > - RDTSC and userspace HPET access > - CPUID? > - 32-bit GDT code segments [huge attack surface] > - 64-bit GDT code segments [probably pointless] > > I would propose a new syscall for this: > > long restrict_userspace(int mode, int type, int value, int flags); > > mode is RESTRICT_SET, RESTRICT_GET, or RESTRICT_LOCK. > > type is RESTRICT_GRND_RANDOM, RESTRICT_PID_SCOPE, RESTRICT_X86_TIMING, etc. > > Value is zero if RESTRICT_GET. Otherwise value is the desired value, > generally 0 or 1. For RESTRICT_PID_SCOPE, value would be > RESTRICT_PID_SCOPE_ANY, RESTRICT_PID_SCOPE_THREADGROUP, or > RESTRICT_PID_SCOPE_SELF. > > flags must be zero. Someday, someone will propose a thread-sync flag. Today, me: proposed :-) > restrict_userspace requires either no_new_privs or CAP_SYS_ADMIN in > the current user namespace. > > Thoughts? > > --Andy > > -- > Andy Lutomirski > AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
