netdev - Re: [RFC v4 07/11] vduse: Introduce VDUSE

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Date:   Wed, 10 Mar 2021 20:58:30 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xie Yongji <xieyongji@...edance.com>, mst@...hat.com,
        stefanha@...hat.com, sgarzare@...hat.com, parav@...dia.com,
        bob.liu@...cle.com, hch@...radead.org, rdunlap@...radead.org,
        willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
        bcrl@...ck.org, corbet@....net
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [RFC v4 07/11] vduse: Introduce VDUSE - vDPA Device in Userspace


On 2021/2/23 7:50 下午, Xie Yongji wrote:
> +
> +	switch (cmd) {
> +	case VDUSE_IOTLB_GET_FD: {
> +		struct vduse_iotlb_entry entry;
> +		struct vhost_iotlb_map *map;
> +		struct vdpa_map_file *map_file;
> +		struct file *f = NULL;
> +
> +		ret = -EFAULT;
> +		if (copy_from_user(&entry, argp, sizeof(entry)))
> +			break;
> +
> +		spin_lock(&dev->iommu_lock);
> +		map = vhost_iotlb_itree_first(dev->iommu, entry.start,
> +					      entry.last);
> +		if (map) {
> +			map_file = (struct vdpa_map_file *)map->opaque;
> +			f = get_file(map_file->file);
> +			entry.offset = map_file->offset;
> +			entry.start = map->start;
> +			entry.last = map->last;
> +			entry.perm = map->perm;
> +		}
> +		spin_unlock(&dev->iommu_lock);
> +		if (!f) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +		if (copy_to_user(argp, &entry, sizeof(entry))) {
> +			fput(f);
> +			ret = -EFAULT;
> +			break;
> +		}
> +		ret = get_unused_fd_flags(perm_to_file_flags(entry.perm));
> +		if (ret < 0) {
> +			fput(f);
> +			break;
> +		}
> +		fd_install(ret, f);


So at least we need to use receice_fd_user() here to give a chance to be 
hooked into security module.

Consider this is bascially a kind of passing file descriptor implicitly. 
We need to be careful if any security stufss is missed.

(Have a quick glance at scm_send/recv, feel ok but need to double check).

Thanks


> +		break;
> +	}