linux-kernel - Re: [PATCH v3 03/16] iommufd/viommu: Add IOMMU_VDEVICE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241017185230.GS3559746@nvidia.com>
Date: Thu, 17 Oct 2024 15:52:30 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, will@...nel.org, joro@...tes.org,
	suravee.suthikulpanit@....com, robin.murphy@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com, shuah@...nel.org,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com,
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com,
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com,
	yi.l.liu@...el.com, aik@....com, patches@...ts.linux.dev
Subject: Re: [PATCH v3 03/16] iommufd/viommu: Add IOMMU_VDEVICE_ALLOC ioctl

On Wed, Oct 09, 2024 at 09:38:15AM -0700, Nicolin Chen wrote:
> +void iommufd_vdevice_destroy(struct iommufd_object *obj)
> +{
> +	struct iommufd_vdevice *old, *vdev =
> +		container_of(obj, struct iommufd_vdevice, obj);
> +	struct iommufd_viommu *viommu = vdev->viommu;
> +	struct iommufd_device *idev = vdev->idev;
> +
> +	if (viommu->ops && viommu->ops->vdevice_free)
> +		viommu->ops->vdevice_free(vdev);
> +
> +	old = xa_cmpxchg(&viommu->vdevs, vdev->id, vdev, NULL, GFP_KERNEL);
> +	if (old)
> +		WARN_ON(old != vdev);
> +
> +	refcount_dec(&viommu->obj.users);
> +	refcount_dec(&idev->obj.users);
> +	idev->vdev = NULL;

This should hold the igroup lock when touching vdev?

> +int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
> +{
> +	struct iommu_vdevice_alloc *cmd = ucmd->cmd;
> +	struct iommufd_vdevice *vdev, *curr;
> +	struct iommufd_viommu *viommu;
> +	struct iommufd_device *idev;
> +	u64 virt_id = cmd->virt_id;
> +	int rc = 0;
> +
> +	if (virt_id > ULONG_MAX)
> +		return -EINVAL;
> +
> +	viommu = iommufd_get_viommu(ucmd, cmd->viommu_id);
> +	if (IS_ERR(viommu))
> +		return PTR_ERR(viommu);
> +
> +	idev = iommufd_get_device(ucmd, cmd->dev_id);
> +	if (IS_ERR(idev)) {
> +		rc = PTR_ERR(idev);
> +		goto out_put_viommu;
> +	}
> +
> +	mutex_lock(&idev->igroup->lock);
> +	if (idev->vdev) {
> +		rc = -EEXIST;
> +		goto out_unlock_igroup;
> +	}

Otherwise this won't work right

> +	if (viommu->ops && viommu->ops->vdevice_alloc)
> +		vdev = viommu->ops->vdevice_alloc(viommu, idev->dev, virt_id);
> +	else
> +		vdev = __iommufd_vdevice_alloc(ucmd->ictx, sizeof(*vdev));
> +	if (IS_ERR(vdev)) {
> +		rc = PTR_ERR(vdev);
> +		goto out_unlock_igroup;
> +	}
> +
> +	vdev->idev = idev;
> +	vdev->id = virt_id;
> +	vdev->viommu = viommu;
> +
> +	idev->vdev = vdev;
> +	refcount_inc(&idev->obj.users);
> +	refcount_inc(&viommu->obj.users);
> +
> +	curr = xa_cmpxchg(&viommu->vdevs, virt_id, NULL, vdev, GFP_KERNEL);
> +	if (curr) {
> +		rc = xa_err(curr) ? : -EBUSY;
> +		goto out_abort;
> +	}
> +
> +	cmd->out_vdevice_id = vdev->obj.id;
> +	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
> +	if (rc)
> +		goto out_abort;
> +	iommufd_object_finalize(ucmd->ictx, &vdev->obj);
> +	goto out_unlock_igroup;
> +
> +out_abort:
> +	iommufd_object_abort_and_destroy(ucmd->ictx, &vdev->obj);

But be mindful of this abort, it doesn't want to be inside the lock if
it also gets the lock.. fail_nth should be updated to cover these new
ioctls to look for tricky things like that

But the design looks OK

Jason