nbd: verify socket is supported during setup

nbd requires socket families to support the shutdown method so the nbd
recv workqueue can be woken up from its sock_recvmsg call. If the socket
does not support the callout we will leave recv works running or get hangs
later when the device or module is removed.

This adds a check during socket connection/reconnection to make sure the
socket being passed in supports the needed callout.

Reported-by: syzbot+24c12fa8d218ed26011a@syzkaller.appspotmail.com
Fixes: e9e006f5fcf2 ("nbd: fix max number of supported devs")
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index e200c7c..a94ee45 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -980,6 +980,25 @@ static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
        return ret;
 }
 
+static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd,
+                                    int *err)
+{
+       struct socket *sock;
+
+       *err = 0;
+       sock = sockfd_lookup(fd, err);
+       if (!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;
+               return NULL;
+       }
+
+       return sock;
+}
+
 static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
                          bool netlink)
 {
@@ -989,7 +1008,7 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
        struct nbd_sock *nsock;
        int err;
 
-       sock = sockfd_lookup(arg, &err);
+       sock = nbd_get_socket(nbd, arg, &err);
        if (!sock)
                return err;
 
@@ -1041,7 +1060,7 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
        int i;
        int err;
 
-       sock = sockfd_lookup(arg, &err);
+       sock = nbd_get_socket(nbd, arg, &err);
        if (!sock)
                return err;