linux-kernel - Re: [PATCH v7 11/12] vduse: Introduce VDUSE

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Message-ID: <YKYBle/F8aOgHO9p@zeniv-ca.linux.org.uk>
Date:   Thu, 20 May 2021 06:28:37 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     mst@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
        sgarzare@...hat.com, parav@...dia.com, hch@...radead.org,
        christian.brauner@...onical.com, rdunlap@...radead.org,
        willy@...radead.org, axboe@...nel.dk, bcrl@...ck.org,
        corbet@....net, mika.penttila@...tfour.com,
        dan.carpenter@...cle.com, joro@...tes.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 11/12] vduse: Introduce VDUSE - vDPA Device in
 Userspace

On Mon, May 17, 2021 at 05:55:12PM +0800, Xie Yongji wrote:

> +	case VDUSE_IOTLB_GET_FD: {
> +		struct vduse_iotlb_entry entry;
> +		struct vhost_iotlb_map *map;
> +		struct vdpa_map_file *map_file;
> +		struct vduse_iova_domain *domain = dev->domain;
> +		struct file *f = NULL;
> +
> +		ret = -EFAULT;
> +		if (copy_from_user(&entry, argp, sizeof(entry)))
> +			break;

			return -EFAULT;
surely?
> +
> +		ret = -EINVAL;
> +		if (entry.start > entry.last)
> +			break;

... and similar here, etc.

> +		spin_lock(&domain->iotlb_lock);
> +		map = vhost_iotlb_itree_first(domain->iotlb,
> +					      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(&domain->iotlb_lock);
> +		ret = -EINVAL;
> +		if (!f)
> +			break;
> +
> +		ret = -EFAULT;
> +		if (copy_to_user(argp, &entry, sizeof(entry))) {
> +			fput(f);
> +			break;
> +		}
> +		ret = receive_fd(f, perm_to_file_flags(entry.perm));
> +		fput(f);
> +		break;

IDGI.  The main difference between receive_fd() and plain old
get_unused_fd_flags() + fd_install() is __receive_sock() call.
Which does nothing whatsoever in case of non-sockets.  Can you
get a socket here?

IOW, why bother with that crap at all, nevermind exporting it?