net: netdevsim: try to close UDP port harness races

syzbot discovered that we remove the debugfs files after we free
the netdev. Try to clean up the relevant dir while the device
is still around.

Reported-by: [e-mail]
Fixes: 424be63ad831 ("netdevsim: add UDP tunnel port offload support")
Reviewed-by: Michal Swiatkowski <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/netdevsim/netdevsim.h

···
 		u32 sleep;
 		u32 __ports[2][NSIM_UDP_TUNNEL_N_PORTS];
 		u32 (*ports)[NSIM_UDP_TUNNEL_N_PORTS];
+		struct dentry *ddir;
 		struct debugfs_u32_array dfs_ports[2];
 	} udp_ports;
 

drivers/net/netdevsim/udp_tunnels.c

···
 	struct net_device *dev = file->private_data;
 	struct netdevsim *ns = netdev_priv(dev);
 
-	memset(ns->udp_ports.ports, 0, sizeof(ns->udp_ports.__ports));
 	rtnl_lock();
-	udp_tunnel_nic_reset_ntf(dev);
+	if (dev->reg_state == NETREG_REGISTERED) {
+		memset(ns->udp_ports.ports, 0, sizeof(ns->udp_ports.__ports));
+		udp_tunnel_nic_reset_ntf(dev);
+	}
 	rtnl_unlock();
 
 	return count;
···
 	else
 		ns->udp_ports.ports = nsim_dev->udp_ports.__ports;
 
-	debugfs_create_u32("udp_ports_inject_error", 0600,
-			   ns->nsim_dev_port->ddir,
+	ns->udp_ports.ddir = debugfs_create_dir("udp_ports",
+						ns->nsim_dev_port->ddir);
+
+	debugfs_create_u32("inject_error", 0600, ns->udp_ports.ddir,
 			   &ns->udp_ports.inject_error);
 
 	ns->udp_ports.dfs_ports[0].array = ns->udp_ports.ports[0];
 	ns->udp_ports.dfs_ports[0].n_elements = NSIM_UDP_TUNNEL_N_PORTS;
-	debugfs_create_u32_array("udp_ports_table0", 0400,
-				 ns->nsim_dev_port->ddir,
+	debugfs_create_u32_array("table0", 0400, ns->udp_ports.ddir,
 				 &ns->udp_ports.dfs_ports[0]);
 
 	ns->udp_ports.dfs_ports[1].array = ns->udp_ports.ports[1];
 	ns->udp_ports.dfs_ports[1].n_elements = NSIM_UDP_TUNNEL_N_PORTS;
-	debugfs_create_u32_array("udp_ports_table1", 0400,
-				 ns->nsim_dev_port->ddir,
+	debugfs_create_u32_array("table1", 0400, ns->udp_ports.ddir,
 				 &ns->udp_ports.dfs_ports[1]);
 
-	debugfs_create_file("udp_ports_reset", 0200, ns->nsim_dev_port->ddir,
+	debugfs_create_file("reset", 0200, ns->udp_ports.ddir,
 			    dev, &nsim_udp_tunnels_info_reset_fops);
 
 	/* Note: it's not normal to allocate the info struct like this!
···
 
 void nsim_udp_tunnels_info_destroy(struct net_device *dev)
 {
+	struct netdevsim *ns = netdev_priv(dev);
+
+	debugfs_remove_recursive(ns->udp_ports.ddir);
 	kfree(dev->udp_tunnel_nic_info);
 	dev->udp_tunnel_nic_info = NULL;
 }

tools/testing/selftests/drivers/net/netdevsim/udp_tunnel_nic.sh

···
 }
 
 function check_table {
-    local path=$NSIM_DEV_DFS/ports/$port/udp_ports_table$1
+    local path=$NSIM_DEV_DFS/ports/$port/udp_ports/table$1
     local -n expected=$2
     local last=$3
 
···
 }
 
 function print_table {
-    local path=$NSIM_DEV_DFS/ports/$port/udp_ports_table$1
+    local path=$NSIM_DEV_DFS/ports/$port/udp_ports/table$1
     read -a have < $path
 
     tree $NSIM_DEV_DFS/
···
     NSIM_NETDEV=`get_netdev_name old_netdevs`
     ip link set dev $NSIM_NETDEV up
 
-    echo 110 > $NSIM_DEV_DFS/ports/$port/udp_ports_inject_error
+    echo 110 > $NSIM_DEV_DFS/ports/$port/udp_ports/inject_error
 
     msg="1 - create VxLANs v6"
     exp0=( 0 0 0 0 )
···
     new_geneve gnv0 20000
 
     msg="2 - destroy GENEVE"
-    echo 2 > $NSIM_DEV_DFS/ports/$port/udp_ports_inject_error
+    echo 2 > $NSIM_DEV_DFS/ports/$port/udp_ports/inject_error
     exp1=( `mke 20000 2` 0 0 0 )
     del_dev gnv0
 
···
     msg="create VxLANs v4"
     new_vxlan vxlan0 10000 $NSIM_NETDEV
 
-    echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports_reset
+    echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports/reset
     check_tables
 
     msg="NIC device goes down"
···
     fi
     check_tables
 
-    echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports_reset
+    echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports/reset
     check_tables
 
     msg="NIC device goes up again"
···
     del_dev vxlan0
     check_tables
 
-    echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports_reset
+    echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports/reset
     check_tables
 
     msg="destroy NIC"
···
 exp0=( `mke 10000 1` `mke 10004 1` 0 `mke 10003 1` )
 del_dev vxlan2
 
-echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports_reset
+echo 1 > $NSIM_DEV_DFS/ports/$port/udp_ports/reset
 check_tables
 
 msg="tunnels destroyed 2"