On Mon, May 15, 2023 at 4:28 PM Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > On 5/15/23 06:05, jeffxu@xxxxxxxxxxxx wrote: > > We're using PKU for in-process isolation to enforce control-flow integrity > > for a JIT compiler. In our threat model, an attacker exploits a > > vulnerability and has arbitrary read/write access to the whole process > > space concurrently to other threads being executed. This attacker can > > manipulate some arguments to syscalls from some threads. > > This all sounds like it hinges on the contents of PKRU in the attacker > thread. > > Could you talk a bit about how the attacker is prevented from running > WRPKRU, XRSTOR or compelling the kernel to write to PKRU like at sigreturn? (resending without html) Since we're using the feature for control-flow integrity, we assume the control-flow is still intact at this point. I.e. the attacker thread can't run arbitrary instructions. * For JIT code, we're going to scan it for wrpkru instructions before writing it to executable memory * For regular code, we only use wrpkru around short critical sections to temporarily enable write access Sigreturn is a separate problem that we hope to solve by adding pkey support to sigaltstack
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