[v1] KVM: x86: fix illegal MP_STATE when in/entering SMM
diff mbox

Message ID 20170322155354.18436-1-david@redhat.com
State New
Headers show

Commit Message

David Hildenbrand March 22, 2017, 3:53 p.m. UTC
If we already entered/are about to enter SMM, don't allow
switching to INIT/SIPI_RECEIVED, otherwise the next call to
kvm_apic_accept_events() will report a warning.

Fixes: cd7764fe9f73 ("KVM: x86: latch INITs while in system management mode")
Cc: stable@vger.kernel.org # 4.2+
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 arch/x86/kvm/x86.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Radim Krčmář March 22, 2017, 4:49 p.m. UTC | #1
2017-03-22 16:53+0100, David Hildenbrand:
> If we already entered/are about to enter SMM, don't allow
> switching to INIT/SIPI_RECEIVED, otherwise the next call to
> kvm_apic_accept_events() will report a warning.
> 
> Fixes: cd7764fe9f73 ("KVM: x86: latch INITs while in system management mode")
> Cc: stable@vger.kernel.org # 4.2+
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 1faf620..7d0ec1b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7355,6 +7355,12 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
>  	    mp_state->mp_state != KVM_MP_STATE_RUNNABLE)
>  		return -EINVAL;
>  
> +	/* INITs are latched while in SMM */
> +	if ((is_smm(vcpu) || vcpu->arch.smi_pending) &&

I think that userspace can still set the mpstate first and then enter
SMM with KVM_SET_VCPU_EVENTS, which would result in the same warning ...
Don't we need a similar check in kvm_vcpu_ioctl_x86_set_vcpu_events()?

Thanks.

> +	    (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED ||
> +	     mp_state->mp_state == KVM_MP_STATE_INIT_RECEIVED))
> +		return -EINVAL;
> +
>  	if (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED) {
>  		vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
>  		set_bit(KVM_APIC_SIPI, &vcpu->arch.apic->pending_events);
> -- 
> 2.9.3
>
Dmitry Vyukov March 23, 2017, 9:49 a.m. UTC | #2
On Wed, Mar 22, 2017 at 5:49 PM, Radim Krčmář <rkrcmar@redhat.com> wrote:
> 2017-03-22 16:53+0100, David Hildenbrand:
>> If we already entered/are about to enter SMM, don't allow
>> switching to INIT/SIPI_RECEIVED, otherwise the next call to
>> kvm_apic_accept_events() will report a warning.
>>
>> Fixes: cd7764fe9f73 ("KVM: x86: latch INITs while in system management mode")
>> Cc: stable@vger.kernel.org # 4.2+
>> Reported-by: Dmitry Vyukov <dvyukov@google.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 1faf620..7d0ec1b 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -7355,6 +7355,12 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
>>           mp_state->mp_state != KVM_MP_STATE_RUNNABLE)
>>               return -EINVAL;
>>
>> +     /* INITs are latched while in SMM */
>> +     if ((is_smm(vcpu) || vcpu->arch.smi_pending) &&
>
> I think that userspace can still set the mpstate first and then enter
> SMM with KVM_SET_VCPU_EVENTS, which would result in the same warning ...
> Don't we need a similar check in kvm_vcpu_ioctl_x86_set_vcpu_events()?
>
> Thanks.
>
>> +         (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED ||
>> +          mp_state->mp_state == KVM_MP_STATE_INIT_RECEIVED))
>> +             return -EINVAL;
>> +
>>       if (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED) {
>>               vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
>>               set_bit(KVM_APIC_SIPI, &vcpu->arch.apic->pending_events);
>> --
>> 2.9.3
>>


This program still triggers the warning in kvm_apic_accept_events with
the patch applied (on top of
093b995e3b55a0ae0670226ddfcb05bfbf0099ae):

https://gist.githubusercontent.com/dvyukov/2a39303347aa417aea2afd9fd99b7086/raw/09693aa7ed78d22b23948c726767f540b2276a99/gistfile1.txt

------------[ cut here ]------------
WARNING: CPU: 3 PID: 2964 at arch/x86/kvm/lapic.c:2461
kvm_apic_accept_events+0x46c/0x550 arch/x86/kvm/lapic.c:2461
CPU: 3 PID: 2964 Comm: a.out Not tainted 4.11.0-rc3+ #365
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x1b8/0x28d lib/dump_stack.c:52
 panic+0x20c/0x423 kernel/panic.c:180
 __warn+0x1c4/0x1e0 kernel/panic.c:541
 warn_slowpath_null+0x2c/0x40 kernel/panic.c:584
 kvm_apic_accept_events+0x46c/0x550 arch/x86/kvm/lapic.c:2461
 vcpu_block arch/x86/kvm/x86.c:7010 [inline]
 vcpu_run arch/x86/kvm/x86.c:7048 [inline]
 kvm_arch_vcpu_ioctl_run+0xefc/0x59e0 arch/x86/kvm/x86.c:7207
 kvm_vcpu_ioctl+0x627/0x1100 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2573
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1af/0x16d0 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x447109
RSP: 002b:00007ffcb458a038 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002b0 RCX: 0000000000447109
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00000000004073f0 R14: 0000000000407480 R15: 0000000000000000
David Hildenbrand March 23, 2017, 10:23 a.m. UTC | #3
> This program still triggers the warning in kvm_apic_accept_events with
> the patch applied (on top of
> 093b995e3b55a0ae0670226ddfcb05bfbf0099ae):
> 
> https://gist.githubusercontent.com/dvyukov/2a39303347aa417aea2afd9fd99b7086/raw/09693aa7ed78d22b23948c726767f540b2276a99/gistfile1.txt
> 
> ------------[ cut here ]------------
> WARNING: CPU: 3 PID: 2964 at arch/x86/kvm/lapic.c:2461
> kvm_apic_accept_events+0x46c/0x550 arch/x86/kvm/lapic.c:2461
> CPU: 3 PID: 2964 Comm: a.out Not tainted 4.11.0-rc3+ #365
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:16 [inline]
>  dump_stack+0x1b8/0x28d lib/dump_stack.c:52
>  panic+0x20c/0x423 kernel/panic.c:180
>  __warn+0x1c4/0x1e0 kernel/panic.c:541
>  warn_slowpath_null+0x2c/0x40 kernel/panic.c:584
>  kvm_apic_accept_events+0x46c/0x550 arch/x86/kvm/lapic.c:2461
>  vcpu_block arch/x86/kvm/x86.c:7010 [inline]
>  vcpu_run arch/x86/kvm/x86.c:7048 [inline]
>  kvm_arch_vcpu_ioctl_run+0xefc/0x59e0 arch/x86/kvm/x86.c:7207
>  kvm_vcpu_ioctl+0x627/0x1100 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2573
>  vfs_ioctl fs/ioctl.c:45 [inline]
>  do_vfs_ioctl+0x1af/0x16d0 fs/ioctl.c:685
>  SYSC_ioctl fs/ioctl.c:700 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: 0033:0x447109
> RSP: 002b:00007ffcb458a038 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00000000004002b0 RCX: 0000000000447109
> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
> RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
> R13: 00000000004073f0 R14: 0000000000407480 R15: 0000000000000000
> 

I think we're seeing what Radim describes. So this is now a different
call order.

The VCPU is set to KVM_MP_STATE_SIPI_RECEIVED (which results in
KVM_MP_STATE_INIT_RECEIVED). Then, KVM_SET_VCPU_EVENTS
is set with KVM_VCPUEVENT_VALID_SMM | KVM_VCPUEVENT_VALID_NMI_PENDING,
enabling SMM.

Calling kvm_apic_accept_events() then will result in a warning on the
next VCPU run.

So the right thing is indeed adding an additional checks for
KVM_SET_VCPU_EVENTS.

Patch
diff mbox

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1faf620..7d0ec1b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7355,6 +7355,12 @@  int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 	    mp_state->mp_state != KVM_MP_STATE_RUNNABLE)
 		return -EINVAL;
 
+	/* INITs are latched while in SMM */
+	if ((is_smm(vcpu) || vcpu->arch.smi_pending) &&
+	    (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED ||
+	     mp_state->mp_state == KVM_MP_STATE_INIT_RECEIVED))
+		return -EINVAL;
+
 	if (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED) {
 		vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
 		set_bit(KVM_APIC_SIPI, &vcpu->arch.apic->pending_events);