On Tue, May 15, 2018 at 02:41:41PM +0300, Boaz Harrosh wrote: > That would be very hard. Because that program would: > - need to be root > - need to start and pretend it is zus Server with the all mount > thread thing, register new filesystem, grab some pmem devices. > - Mount the said filesystem on said pmem. Create core-pinned ZT threads > for all CPUs, start accepting IO. > - And only then it can start leaking the pointer and do bad things. All of these things you've done for me by writing zus Server. All I have to do now is compromise zus Server. > The bad things it can do to the application, not to the Kernel. > And as a full filesystem it can do those bad things to the application > through the front door directly not needing the mismatch tlb at all. That's not true. When I have a TLB entry that points to a page of kernel ram, I can do almost anything, depending on what the kernel decides to do with that ram next. Maybe it's page cache again, in which case I can affect whatever application happens to get it allocated. Maybe it's a kmalloc page next, in which case I can affect any part of the kernel. Maybe it's a page table, then I can affect any process. > That said. It brings up a very important point that I wanted to talk about. > In this design the zuf(Kernel) and the zus(um Server) are part of the distribution. > I would like to have the zus module be signed by the distro's Kernel's key and > checked on loadtime. I know there is an effort by Redhat guys to try and sign all > /sbin/* servers and have Kernel check these. So this is not the first time people > have thought about that. You're getting dangerously close to admitting that the entire point of this exercise is so that you can link non-GPL NetApp code into the kernel in clear violation of the GPL.
