On Fri, Apr 16, 2021 at 06:00:38PM +0200, Christian Brauner wrote:
> (dma_buf_fd() seems like another good candidate. But again, I don't have
> any plans to shove this down anyone's throat.)
Sure, there are candidates for such a helper. Just as there are legitimate
users of anon_inode_getfd().
However, it is *NOT* something we can use as a vehicle for some hooks (pardon
the obscenity); it won't be consistently used in all cases - it simply is not
feasible for many of the fd_install() users.
Incidentally, looking at the user of receive_fd_user(), I would say that it
would be easier to follow in this form:
case VDUSE_IOTLB_GET_ENTRY: {
struct vduse_iotlb_entry entry;
struct vhost_iotlb_map *map;
struct vduse_iova_domain *domain = dev->domain;
struct file *f = NULL;
if (copy_from_user(&entry, argp, sizeof(entry)))
return -EFAULT;
entry.fd = get_unused_fd_flags(perm_to_file_flags(entry.perm));
if (entry.fd < 0)
return entry.fd;
spin_lock(&domain->iotlb_lock);
map = vhost_iotlb_itree_first(domain->iotlb,
entry.start, entry.start + 1);
if (map) {
struct vdpa_map_file *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);
if (!f) {
put_unused_fd(entry.fd);
return -EINVAL;
}
if (copy_to_user(argp, &entry, sizeof(entry))) {
put_unused_fd(entry.fd);
fput(f);
return -EFAULT;
}
// point of no return
fd_install(entry.fd, f);
return 0;
}
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