On Sun, Jan 15, 2017 at 8:18 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: >> 2017-01-02 11:23+0100, Dmitry Vyukov: >>> Hello, >>> >>> I've got the following warning while running syzkaller fuzzer: >>> >>> WARNING: CPU: 2 PID: 13257 at arch/x86/kvm/vmx.c:8633 >>> vmx_handle_exit+0x262b/0x38b0 arch/x86/kvm/vmx.c:8633 >>> vmx: unexpected exit reason 0xb >>> CPU: 2 PID: 13257 Comm: syz-executor7 Not tainted 4.10.0-rc1+ #118 >>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >>> Call Trace: >>> __dump_stack lib/dump_stack.c:15 [inline] >>> dump_stack+0x292/0x3a2 lib/dump_stack.c:51 >>> panic+0x1cb/0x3a9 kernel/panic.c:179 >>> __warn+0x1c4/0x1e0 kernel/panic.c:539 >>> warn_slowpath_fmt+0xc5/0x100 kernel/panic.c:562 >>> vmx_handle_exit+0x262b/0x38b0 arch/x86/kvm/vmx.c:8633 >>> vcpu_enter_guest arch/x86/kvm/x86.c:6884 [inline] >>> vcpu_run arch/x86/kvm/x86.c:6943 [inline] >>> kvm_arch_vcpu_ioctl_run+0xf3d/0x45f0 arch/x86/kvm/x86.c:7101 >>> kvm_vcpu_ioctl+0x673/0x1120 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2569 >>> vfs_ioctl fs/ioctl.c:43 [inline] >>> do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683 >>> SYSC_ioctl fs/ioctl.c:698 [inline] >>> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689 >>> entry_SYSCALL_64_fastpath+0x1f/0xc2 >>> RIP: 0033:0x4438a9 >>> RSP: 002b:00007f935aa2fb58 EFLAGS: 00000286 ORIG_RAX: 0000000000000010 >>> RAX: ffffffffffffffda RBX: 0000000000000015 RCX: 00000000004438a9 >>> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000015 >>> RBP: 00000000006ddb30 R08: 0000000000000000 R09: 0000000000000000 >>> R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000700000 >>> R13: 0000000000000006 R14: 0000000000000015 R15: 0000000020014000 >>> Dumping ftrace buffer: >>> (ftrace buffer empty) >>> Kernel Offset: disabled >>> >>> Exit reason 0xb is GETSEC instruction. This does not look harmful as >>> it is handled as #UD. But I think we should print a single line >>> message regarding non-emulated instruction as in other cases, just to >>> not scare cloud admins and to make syzkaller ignore it. >>> >>> FTR, a raw reproducer is here: >>> https://gist.githubusercontent.com/dvyukov/c762f6ea04ebbba49cdee0a6caca31b4/raw/f21deb04cdc70ae74100c12447d71bb0cd2025c7/gistfile1.txt >> >> I can't reproduce -- maybe a nested bug, which will take a while to >> figure out. Still, host dump at that point is useless, so the change >> makes sense. >> >> A guest dump would be useful (e.g. I think that GETSEC should not exit > > Thanks! > > I had to disable dump_vmcs locally because it constantly produces tons > of output even when no bugs happen. > If you really-really need it, I can enable dump_vmcs and re-reproduce the bug. > > >> if guest CR4.SMX is disabled), but just giving the error is about as >> good and we want something short and rate-limited if the message can be >> trigerred by a guest in production ... >> ---8<--- >> We never needed the call trace and we better rate-limit if it can be >> triggered by a guest. >> >> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx> >> --- >> arch/x86/kvm/vmx.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index a236decb81e4..7cd606daa01e 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -8595,7 +8595,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) >> && kvm_vmx_exit_handlers[exit_reason]) >> return kvm_vmx_exit_handlers[exit_reason](vcpu); >> else { >> - WARN_ONCE(1, "vmx: unexpected exit reason 0x%x\n", exit_reason); >> + vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", >> + exit_reason); >> kvm_queue_exception(vcpu, UD_VECTOR); >> return 1; >> } >> -- >> 2.11.0 >> Was this ever merged? Still happens for me.
