Re: [PATCH v5 3/9] mshv: Introduce basic mshv bridge device for VFIO to build upon

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The `mshv_vfio` structure is allocated without `__GFP_ACCOUNT`, allowing a container to allocate kernel memory without being charged to its memory cgroup limit.
--

--- Patch [3]: [PATCH v5 3/9] mshv: Introduce basic mshv bridge device for VFIO to build upon ---
commit c0b4902f22a48f131a914dbd4da4237e2be4826b
Author: Mukesh R <mrathor@linux.microsoft.com>

mshv: Introduce basic mshv bridge device for VFIO to build upon

This commit adds a new file to implement a basic VFIO-MSHV bridge pseudo
device. It provides the foundation for VFIO integration in the MSHV
framework, adapting concepts from the KVM-VFIO bridge.

> diff --git a/drivers/hv/mshv_vfio.c b/drivers/hv/mshv_vfio.c
> new file mode 100644
> index 0000000000000..92cfbaef0328d
> --- /dev/null
> +++ b/drivers/hv/mshv_vfio.c

[ ... ]

> +static long mshv_vfio_create_device(struct mshv_device *mshvdev)
> +{
> +	struct mshv_device *tmp;
> +	struct mshv_vfio *mshv_vfio;
> +
> +	/* Only one VFIO "device" per VM */
> +	hlist_for_each_entry(tmp, &mshvdev->device_pt->pt_devices,
> +			     device_ptnode)
> +		if (tmp->device_ops == &mshv_vfio_device_ops)
> +			return -EBUSY;
> +
> +	mshv_vfio = kzalloc_obj(*mshv_vfio);

[Severity: Medium]
Should this allocation include __GFP_ACCOUNT?

When a user space process creates a new MSHV VFIO device, it triggers
mshv_vfio_create_device(). The kzalloc_obj() macro defaults to GFP_KERNEL,
which omits the necessary accounting flags.

This allows a container to allocate kernel memory without being charged to
its memory cgroup limit.

> +	if (mshv_vfio == NULL)
> +		return -ENOMEM;
> +
> +	INIT_LIST_HEAD(&mshv_vfio->file_list);
> +	mutex_init(&mshv_vfio->lock);
> +
> +	mshvdev->device_private = mshv_vfio;
> +
> +	return 0;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260731223427.2554388-1-mrathor@linux.microsoft.com?part=3