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: syzbot+2e5de9e3ab986b71d2bf@syzkaller.appspotmail.com
Fixes: 424be63ad831 ("netdevsim: add UDP tunnel port offload support")
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/20250122224503.762705-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 23 insertions, 17 deletions

diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index dcf073bc4802e..96d54c08043d3 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -134,6 +134,7 @@ struct netdevsim {
 		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;
 
diff --git a/drivers/net/netdevsim/udp_tunnels.c b/drivers/net/netdevsim/udp_tunnels.c
index 02dc3123eb6c1..640b4983a9a0d 100644
--- a/drivers/net/netdevsim/udp_tunnels.c
+++ b/drivers/net/netdevsim/udp_tunnels.c
@@ -112,9 +112,11 @@ nsim_udp_tunnels_info_reset_write(struct file *file, const char __user *data,
 	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;
@@ -144,23 +146,23 @@ int nsim_udp_tunnels_info_create(struct nsim_dev *nsim_dev,
 	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!
@@ -196,6 +198,9 @@ int nsim_udp_tunnels_info_create(struct nsim_dev *nsim_dev,
 
 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;
 }
diff --git a/tools/testing/selftests/drivers/net/netdevsim/udp_tunnel_nic.sh b/tools/testing/selftests/drivers/net/netdevsim/udp_tunnel_nic.sh
index 384cfa3d38a6c..92c2f0376c081 100755
--- a/tools/testing/selftests/drivers/net/netdevsim/udp_tunnel_nic.sh
+++ b/tools/testing/selftests/drivers/net/netdevsim/udp_tunnel_nic.sh
@@ -142,7 +142,7 @@ function pre_ethtool {
 }
 
 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
 
@@ -212,7 +212,7 @@ function check_tables {
 }
 
 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/
@@ -641,7 +641,7 @@ for port in 0 1; do
     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 )
@@ -663,7 +663,7 @@ for port in 0 1; do
     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
 
@@ -764,7 +764,7 @@ for port in 0 1; do
     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"
@@ -775,7 +775,7 @@ for port in 0 1; do
     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"
@@ -789,7 +789,7 @@ for port in 0 1; do
     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"
@@ -896,7 +896,7 @@ msg="vacate VxLAN in overflow table"
 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"