tun: avoid calling xdp_rxq_info_unreg() twice

Similarly to tx ring, xdp_rxq_info is only registered
when !tfile->detached, so we need to avoid calling
xdp_rxq_info_unreg() twice too. The helper tun_cleanup_tx_ring()
already checks for this properly, so it is correct to put
xdp_rxq_info_unreg() just inside there.

Reported-by: syzbot+1c788d7ce0f0888f1d7f@syzkaller.appspotmail.com
Fixes: 8565d26bcb2f ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net")
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -774,14 +774,12 @@ static void tun_detach_all(struct net_device *dev)
 		tun_napi_del(tun, tfile);
 		/* Drop read queue */
 		tun_queue_purge(tfile);
-		xdp_rxq_info_unreg(&tfile->xdp_rxq);
 		sock_put(&tfile->sk);
 		tun_cleanup_tx_ring(tfile);
 	}
 	list_for_each_entry_safe(tfile, tmp, &tun->disabled, next) {
 		tun_enable_queue(tfile);
 		tun_queue_purge(tfile);
-		xdp_rxq_info_unreg(&tfile->xdp_rxq);
 		sock_put(&tfile->sk);
 		tun_cleanup_tx_ring(tfile);
 	}