On Sun, Oct 26, 2014 at 10:18 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Sun, Oct 26, 2014 at 10:02:16AM -0700, Andy Lutomirski wrote: >> If an attacker can cause a controlled kernel stack overflow, >> overwriting the restart block is a very juicy exploit target. >> Moving the restart block to struct task_struct prevents this type of >> exploit. > > The hell it does. In a _lot_ of cases current is current_thread_info()->task, > which makes your variant just as vulnerable, in addition to being (slightly) > more costly. I never said it was the *only* juicy target, but we can fix the rest, too. Also, I suspect that overwriting task could be harder to exploit. First, you need to avoid crashing, and second, on systems with SMAP or similar protection, you need to make task point somewhere that contains a useful exploit payload. We could probably get rid of thread_info's task pointer on x86, too -- it's not used by get_current() any more. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
