Re: [syzbot] Re: [syzbot] [net?] WARNING in nsim_udp_tunnel_set_port

[syzbot <syzbot+2e5de9e3ab986b71d2bf@syzkaller.appspotmail.com>]

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***

Subject: Re: [syzbot] [net?] WARNING in nsim_udp_tunnel_set_port
Author: kuba@kernel.org

On Wed, 15 Jan 2025 06:42:22 -0800 syzbot wrote:
> HEAD commit:    63676eefb7a0 Merge tag 'sched_ext-for-6.13-rc5-fixes' of g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1336e418580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f
> dashboard link: https://syzkaller.appspot.com/bug?extid=2e5de9e3ab986b71d2bf
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17cfb1c4580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13ac4edf980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ba5dd9f6cf65/disk-63676eef.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/290bc4e6d798/vmlinux-63676eef.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/561f22e07925/bzImage-63676eef.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+2e5de9e3ab986b71d2bf@syzkaller.appspotmail.com

#syz test

diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index dcf073bc4802..96d54c08043d 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 02dc3123eb6c..cc8cec23ca7e 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;
@@ -160,7 +162,8 @@ int nsim_udp_tunnels_info_create(struct nsim_dev *nsim_dev,
 				 ns->nsim_dev_port->ddir,
 				 &ns->udp_ports.dfs_ports[1]);
 
-	debugfs_create_file("udp_ports_reset", 0200, ns->nsim_dev_port->ddir,
+	ns->udp_ports.ddir =
+		debugfs_create_file("udp_ports_reset", 0200, ns->nsim_dev_port->ddir,
 			    dev, &nsim_udp_tunnels_info_reset_fops);
 
 	/* Note: it's not normal to allocate the info struct like this!
@@ -196,6 +199,9 @@ 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(ns->udp_ports.ddir);
 	kfree(dev->udp_tunnel_nic_info);
 	dev->udp_tunnel_nic_info = NULL;
 }