2020-04-16 20:45:13

by Jon Cargille

Subject: [PATCH] KVM: Remove CREATE_IRQCHIP/SET_PIT2 race

From: Steve Rutherford <[email protected]>

Fixes a NULL pointer dereference, caused by the PIT firing an interrupt
before the interrupt table has been initialized.

SET_PIT2 can race with the creation of the IRQchip. In particular,
if SET_PIT2 is called with a low PIT timer period (after the creation of
the IOAPIC, but before the instantiation of the irq routes), the PIT can
fire an interrupt at an uninitialized table.

Signed-off-by: Steve Rutherford <[email protected]>
Signed-off-by: Jon Cargille <[email protected]>
Reviewed-by: Jim Mattson <[email protected]>
---
arch/x86/kvm/x86.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 027dfd278a973..3cc3f673785c8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5049,10 +5049,13 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&u.ps, argp, sizeof(u.ps)))
goto out;
+ mutex_lock(&kvm->lock);
r = -ENXIO;
if (!kvm->arch.vpit)
- goto out;
+ goto set_pit_out;
r = kvm_vm_ioctl_set_pit(kvm, &u.ps);
+set_pit_out:
+ mutex_unlock(&kvm->lock);
break;
}
case KVM_GET_PIT2: {
@@ -5072,10 +5075,13 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&u.ps2, argp, sizeof(u.ps2)))
goto out;
+ mutex_lock(&kvm->lock);
r = -ENXIO;
if (!kvm->arch.vpit)
- goto out;
+ goto set_pit2_out;
r = kvm_vm_ioctl_set_pit2(kvm, &u.ps2);
+set_pit2_out:
+ mutex_unlock(&kvm->lock);
break;
}
case KVM_REINJECT_CONTROL: {
--
2.26.0.110.g2183baf09c-goog

2020-04-17 15:08:38

by Paolo Bonzini

Subject: Re: [PATCH] KVM: Remove CREATE_IRQCHIP/SET_PIT2 race

On 16/04/20 21:11, Jon Cargille wrote:
> From: Steve Rutherford <[email protected]>
>
> Fixes a NULL pointer dereference, caused by the PIT firing an interrupt
> before the interrupt table has been initialized.
>
> SET_PIT2 can race with the creation of the IRQchip. In particular,
> if SET_PIT2 is called with a low PIT timer period (after the creation of
> the IOAPIC, but before the instantiation of the irq routes), the PIT can
> fire an interrupt at an uninitialized table.
>
> Signed-off-by: Steve Rutherford <[email protected]>
> Signed-off-by: Jon Cargille <[email protected]>
> Reviewed-by: Jim Mattson <[email protected]>
> ---
> arch/x86/kvm/x86.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 027dfd278a973..3cc3f673785c8 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5049,10 +5049,13 @@ long kvm_arch_vm_ioctl(struct file *filp,
> r = -EFAULT;
> if (copy_from_user(&u.ps, argp, sizeof(u.ps)))
> goto out;
> + mutex_lock(&kvm->lock);
> r = -ENXIO;
> if (!kvm->arch.vpit)
> - goto out;
> + goto set_pit_out;
> r = kvm_vm_ioctl_set_pit(kvm, &u.ps);
> +set_pit_out:
> + mutex_unlock(&kvm->lock);
> break;
> }
> case KVM_GET_PIT2: {
> @@ -5072,10 +5075,13 @@ long kvm_arch_vm_ioctl(struct file *filp,
> r = -EFAULT;
> if (copy_from_user(&u.ps2, argp, sizeof(u.ps2)))
> goto out;
> + mutex_lock(&kvm->lock);
> r = -ENXIO;
> if (!kvm->arch.vpit)
> - goto out;
> + goto set_pit2_out;
> r = kvm_vm_ioctl_set_pit2(kvm, &u.ps2);
> +set_pit2_out:
> + mutex_unlock(&kvm->lock);
> break;
> }
> case KVM_REINJECT_CONTROL: {
>

Queued, thanks.

Paolo