linux-kernel - Re: [PATCH 2/9] KVM: arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST

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Date:   Wed, 6 Jan 2021 17:12:50 +0000
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     Eric Auger <eric.auger@...hat.com>, eric.auger.pro@...il.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, maz@...nel.org, drjones@...hat.com
Cc:     james.morse@....com, julien.thierry.kdev@...il.com,
        suzuki.poulose@....com, shuah@...nel.org, pbonzini@...hat.com
Subject: Re: [PATCH 2/9] KVM: arm64: Fix KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION
 read

Hi Eric,

The patch looks correct to me. kvm_vgic_addr() masks out all the bits except index
from addr, so we don't need to do it in vgic_get_common_attr():

Reviewed-by: Alexandru Elisei <alexandru.elisei@....com>

One nitpick below.

On 12/12/20 6:50 PM, Eric Auger wrote:
> The doc says:
> "The characteristics of a specific redistributor region can
>  be read by presetting the index field in the attr data.
>  Only valid for KVM_DEV_TYPE_ARM_VGIC_V3"
>
> Unfortunately the existing code fails to read the input attr data
> and thus the index always is 0.

addr is allocated on the stack, I don't think it will always be 0.

Thanks,
Alex
>
> Fixes: 04c110932225 ("KVM: arm/arm64: Implement KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION")
> Cc: stable@...r.kernel.org#v4.17+
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  arch/arm64/kvm/vgic/vgic-kvm-device.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
> index 44419679f91a..2f66cf247282 100644
> --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
> +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
> @@ -226,6 +226,9 @@ static int vgic_get_common_attr(struct kvm_device *dev,
>  		u64 addr;
>  		unsigned long type = (unsigned long)attr->attr;
>  
> +		if (copy_from_user(&addr, uaddr, sizeof(addr)))
> +			return -EFAULT;
> +
>  		r = kvm_vgic_addr(dev->kvm, type, &addr, false);
>  		if (r)
>  			return (r == -ENODEV) ? -ENXIO : r;