On Mon, Jul 1, 2019 at 8:43 PM Andy Lutomirski <l...@kernel.org> wrote: > > In -tip, if FSGSBASE and PTI are on, the kernel crashes if SYSENTER > happens with TF set. It also crashes under if a non-NMI paranoid > entry happens for any other reason from kernel mode with user GSBASE > and user CR3, e.g. due to MOV SS shenanigans. > > This series fixes the bug. It also adds another test to make sure > we exercise SYSENTER with TF set regardless of what vendor's CPU > we're on, although the test isn't needed to detect the bug: the > single_step_syscall_32 and mov_ss_trap_* tests also trigger it. And > it compiles ignore_sysret out on IA32_EMULATION kernels -- I wasted > a couple minutes while debugging this wondering whether I was > accidentally triggering ignore_sysret.
I forgot to mention: even with this applied, the x86/cpu tree is not ready for prime time. The fsgsbase test case fails on released kernels and crashes on x86/cpu. I haven't gotten to the bottom of it yet. The test code looks a bit dubious, but that doesn't necessarily mean the kernel is okay.
