Re: [PATCH v3 1/4] KVM: arm64: vgic-its: Add a data length check in vgic_its_save_*

[Marc Zyngier <maz@kernel.org>]

On Wed, 06 Nov 2024 08:30:32 +0000,
Jing Zhang <jingzhangos@google.com> wrote:
> 
> From: Kunkun Jiang <jiangkunkun@huawei.com>
> 
> In all the vgic_its_save_*() functinos, they do not check whether
> the data length is 8 bytes before calling vgic_write_guest_lock.
> This patch adds the check. To prevent the kernel from being blown up
> when the fault occurs, KVM_BUG_ON() is used. And the other BUG_ON()s
> are replaced together.
> 
> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> Signed-off-by: Jing Zhang <jingzhangos@google.com>
> ---
>  arch/arm64/kvm/vgic/vgic-its.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
> index ba945ba78cc7..2381bc5ce544 100644
> --- a/arch/arm64/kvm/vgic/vgic-its.c
> +++ b/arch/arm64/kvm/vgic/vgic-its.c
> @@ -2095,6 +2095,10 @@ static int vgic_its_save_ite(struct vgic_its *its, struct its_device *dev,
>  	       ((u64)ite->irq->intid << KVM_ITS_ITE_PINTID_SHIFT) |
>  		ite->collection->collection_id;
>  	val = cpu_to_le64(val);
> +
> +	if (KVM_BUG_ON(ite_esz != sizeof(val), kvm))
> +		return -EINVAL;
> +
>  	return vgic_write_guest_lock(kvm, gpa, &val, ite_esz);
>  }
>  
> @@ -2250,6 +2254,10 @@ static int vgic_its_save_dte(struct vgic_its *its, struct its_device *dev,
>  	       (itt_addr_field << KVM_ITS_DTE_ITTADDR_SHIFT) |
>  		(dev->num_eventid_bits - 1));
>  	val = cpu_to_le64(val);
> +
> +	if (KVM_BUG_ON(dte_esz != sizeof(val), kvm))
> +		return -EINVAL;
> +
>  	return vgic_write_guest_lock(kvm, ptr, &val, dte_esz);
>  }
>  
> @@ -2431,12 +2439,17 @@ static int vgic_its_save_cte(struct vgic_its *its,
>  			     struct its_collection *collection,
>  			     gpa_t gpa, int esz)
>  {
> +	struct kvm *kvm = its->dev->kvm;

nit: just use its->dev->kvm consistently, as this is what we are
already doing in this function.

	M.

-- 
Without deviation from the norm, progress is not possible.