netdev - [PATCH net 2/2] hamradio: ignore ops-locked netdevs

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Message-ID: <20250806213726.1383379-2-sdf@fomichev.me>
Date: Wed,  6 Aug 2025 14:37:26 -0700
From: Stanislav Fomichev <sdf@...ichev.me>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	andrew+netdev@...n.ch,
	ms@....tdt.de,
	ast@...nel.org,
	daniel@...earbox.net,
	hawk@...nel.org,
	john.fastabend@...il.com,
	sdf@...ichev.me,
	aleksander.lobakin@...el.com,
	linux-kernel@...r.kernel.org,
	linux-x25@...r.kernel.org,
	bpf@...r.kernel.org,
	syzbot+e6300f66a999a6612477@...kaller.appspotmail.com
Subject: [PATCH net 2/2] hamradio: ignore ops-locked netdevs

Syzkaller managed to trigger lock dependency in xsk_notify via
register_netdevice. As discussed in [0], using register_netdevice
in the notifiers is problematic so skip adding hamradio for ops-locked
devices.

       xsk_notifier+0x89/0x230 net/xdp/xsk.c:1664
       notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
       call_netdevice_notifiers net/core/dev.c:2281 [inline]
       unregister_netdevice_many_notify+0x14d7/0x1ff0 net/core/dev.c:12156
       unregister_netdevice_many net/core/dev.c:12219 [inline]
       unregister_netdevice_queue+0x33c/0x380 net/core/dev.c:12063
       register_netdevice+0x1689/0x1ae0 net/core/dev.c:11241
       bpq_new_device drivers/net/hamradio/bpqether.c:481 [inline]
       bpq_device_event+0x491/0x600 drivers/net/hamradio/bpqether.c:523
       notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
       call_netdevice_notifiers net/core/dev.c:2281 [inline]
       __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
       netif_change_flags+0xe8/0x1a0 net/core/dev.c:9608
       dev_change_flags+0x130/0x260 net/core/dev_api.c:68
       devinet_ioctl+0xbb4/0x1b50 net/ipv4/devinet.c:1200
       inet_ioctl+0x3c0/0x4c0 net/ipv4/af_inet.c:1001

0: https://lore.kernel.org/netdev/20250625140357.6203d0af@kernel.org/
Fixes: 4c975fd70002 ("net: hold instance lock during NETDEV_REGISTER/UP")
Suggested-by: Jakub Kicinski <kuba@...nel.org>
Reported-by: syzbot+e6300f66a999a6612477@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=e6300f66a999a6612477
Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
---
 drivers/net/hamradio/bpqether.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/hamradio/bpqether.c b/drivers/net/hamradio/bpqether.c
index 0e0fe32d2da4..045c5177262e 100644
--- a/drivers/net/hamradio/bpqether.c
+++ b/drivers/net/hamradio/bpqether.c
@@ -138,7 +138,7 @@ static inline struct net_device *bpq_get_ax25_dev(struct net_device *dev)
 
 static inline int dev_is_ethdev(struct net_device *dev)
 {
-	return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
+	return dev->type == ARPHRD_ETHER && !netdev_need_ops_lock(dev);
 }
 
 /* ------------------------------------------------------------------------ */
-- 
2.50.1