On Fri, 2019-06-07 at 11:58 -0700, Dave Hansen wrote: > On 6/7/19 11:29 AM, Andy Lutomirski wrote: > ... > > > I think this new MSR probably needs to get included in oops output when > > > CET is enabled. > > > > This shouldn’t be able to OOPS because it only happens at CPL 3, > > right? We should put it into core dumps, though. > > Good point. > > Yu-cheng, can you just confirm that the bitmap can't be referenced in > ring-0, no matter what? We should also make sure that no funny business > happens if we put an address in the bitmap that faults, or is > non-canonical. Do we have any self-tests for that?
Yes, the bitmap is user memory, but the kernel can still get to it (e.g. copy_from_user()). We can do more check on the address. > > Let's say userspace gets a fault on this. Do they have the > introspection capability to figure out why they faulted, say in their > signal handler? The bitmap address is kept by the application; the kernel won't provide it again to user-space. In the signal handler, the app can find out from its own record. [...]
