On Fri, Jan 13, 2017 at 6:59 PM, Radim Krčmář <rkrcmar@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 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
