nbd: restrict sockets to TCP and UDP

JIRA: https://issues.redhat.com/browse/RHEL-121713

commit 9f7c02e
Author: Eric Dumazet <edumazet@google.com>
Date:   Tue Sep 9 13:22:43 2025 +0000

    nbd: restrict sockets to TCP and UDP

    Recently, syzbot started to abuse NBD with all kinds of sockets.

    Commit cf1b232 ("nbd: verify socket is supported during setup")
    made sure the socket supported a shutdown() method.

    Explicitely accept TCP and UNIX stream sockets.

    Fixes: cf1b232 ("nbd: verify socket is supported during setup")
    Reported-by: syzbot+e1cd6bd8493060bd701d@syzkaller.appspotmail.com
    Closes: https://lore.kernel.org/netdev/CANn89iJ+76eE3A_8S_zTpSyW5hvPRn6V57458hCZGY5hbH_bFA@mail.gmail.com/T/#m081036e8747cd7e2626c1da5d78c8b9d1e55b154
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Mike Christie <mchristi@redhat.com>
    Cc: Richard W.M. Jones <rjones@redhat.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Yu Kuai <yukuai1@huaweicloud.com>
    Cc: linux-block@vger.kernel.org
    Cc: nbd@other.debian.org
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Author: Ming Lei

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;