Re: [syzbot] [net?] [nfc?] WARNING in nfc_rfkill_set_block

[Hillf Danton <hdanton@sina.com>]

> Date: Sun, 31 Aug 2025 00:02:33 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    c8bc81a52d5a Merge tag 'arm64-fixes' of git://git.kernel.o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1508ce34580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bd9738e00c1bbfb4
> dashboard link: https://syzkaller.appspot.com/bug?extid=535bbe83dfc3ae8d4be3
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11019a62580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1308ce34580000

Test Kim's patch.

#syz test

--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -1154,6 +1154,7 @@ EXPORT_SYMBOL(nfc_register_device);
 void nfc_unregister_device(struct nfc_dev *dev)
 {
 	int rc;
+	struct rfkill *rfk = NULL;
 
 	pr_debug("dev_name=%s\n", dev_name(&dev->dev));
 
@@ -1163,14 +1164,18 @@ void nfc_unregister_device(struct nfc_dev *dev)
 			 "was removed\n", dev_name(&dev->dev));
 
 	device_lock(&dev->dev);
+	dev->shutting_down = true;
 	if (dev->rfkill) {
-		rfkill_unregister(dev->rfkill);
-		rfkill_destroy(dev->rfkill);
+		rfk = dev->rfkill;
 		dev->rfkill = NULL;
 	}
-	dev->shutting_down = true;
 	device_unlock(&dev->dev);
 
+	if (rfk) {
+		rfkill_unregister(rfk);
+		rfkill_destroy(rfk);
+	}
+
 	if (dev->ops->check_presence) {
 		timer_delete_sync(&dev->check_pres_timer);
 		cancel_work_sync(&dev->check_pres_work);
--