On Tue, Sep 09, 2025 at 01:22:43PM +0000, Eric Dumazet wrote:
> Recently, syzbot started to abuse NBD with all kinds of sockets.
>
> Commit cf1b2326b734 ("nbd: verify socket is supported during setup")
> made sure the socket supported a shutdown() method.
>
> Explicitely accept TCP and UNIX stream sockets.
I'm not clear what the actual problem is, but I will say that libnbd &
nbdkit (which are another NBD client & server, interoperable with the
kernel) we support and use NBD over vsock[1]. And we could support
NBD over pretty much any stream socket (Infiniband?) [2].
[1] https://libguestfs.org/nbd_aio_connect_vsock.3.html
https://libguestfs.org/nbdkit-service.1.html#AF_VSOCK
[2] https://libguestfs.org/nbd_connect_socket.3.html
TCP and Unix domain sockets are by far the most widely used, but I
don't think it's fair to exclude other socket types.
Rich.
> Fixes: cf1b2326b734 ("nbd: verify socket is supported during setup")
> Reported-by: syzbot+e1cd6bd8493060bd701d@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://lore.kernel.org/netdev/CANn89iJ+76eE3A_8S_zTpSyW5hvPRn6V57458hCZGY5hbH_bFA@xxxxxxxxxxxxxx/T/#m081036e8747cd7e2626c1da5d78c8b9d1e55b154
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Mike Christie <mchristi@xxxxxxxxxx>
> Cc: Richard W.M. Jones <rjones@xxxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>
> Cc: linux-block@xxxxxxxxxxxxxxx
> Cc: nbd@xxxxxxxxxxxxxxxx
> ---
> drivers/block/nbd.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 6463d0e8d0cef71e73e67fecd16de4dec1c75da7..87b0b78249da3325023949585f4daf40486c9692 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1217,6 +1217,14 @@ static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd,
> if (!sock)
> return NULL;
>
> + if (!sk_is_tcp(sock->sk) &&
> + !sk_is_stream_unix(sock->sk)) {
> + dev_err(disk_to_dev(nbd->disk), "Unsupported socket: should be TCP or UNIX.\n");
> + *err = -EINVAL;
> + sockfd_put(sock);
> + return NULL;
> + }
> +
> if (sock->ops->shutdown == sock_no_shutdown) {
> dev_err(disk_to_dev(nbd->disk), "Unsupported socket: shutdown callout must be supported.\n");
> *err = -EINVAL;
> --
> 2.51.0.384.g4c02a37b29-goog
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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