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 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
