Re: [syzbot] [net?] [nfc?] WARNING: locking bug in nci_close_device (2)

[Hillf Danton]

On Wed, 03 Apr 2024 12:49:25 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1201b6d3180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  fe46a7dd189e

--- x/net/nfc/nci/core.c
+++ y/net/nfc/nci/core.c
@@ -560,6 +560,10 @@ static int nci_close_device(struct nci_d
 	 */
 	mutex_lock(&ndev->req_lock);
 
+	if (test_and_set_bit(NCI_UNREG +1, &ndev->flags)) {
+		mutex_unlock(&ndev->req_lock);
+		return 0;
+	}
 	if (!test_and_clear_bit(NCI_UP, &ndev->flags)) {
 		/* Need to flush the cmd wq in case
 		 * there is a queued/running cmd_work
@@ -601,6 +605,7 @@ static int nci_close_device(struct nci_d
 
 	/* Clear flags except NCI_UNREG */
 	ndev->flags &= BIT(NCI_UNREG);
+	set_bit(NCI_UNREG +1, &ndev->flags);
 
 	mutex_unlock(&ndev->req_lock);
 
--