linux-kernel - Re: [usb?] possible deadlock in chaoskey

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Message-ID: <tencent_3212D5C64009A62EE86ED08C8467FD46D606@qq.com>
Date: Wed,  9 Oct 2024 16:43:38 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+685e14d04fe35692d3bc@...kaller.appspotmail.com
Cc: gregkh@...uxfoundation.org,
	keithp@...thp.com,
	linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [usb?] possible deadlock in chaoskey_open

delay get the chaoskey_list_lock, avoid to circular locking dependency
chaoskey_release has a wrong logic lock for chaoskey_list_lock, it need unlock.

#syz test

diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
index e8b63df5f975..225863321dc4 100644
--- a/drivers/usb/misc/chaoskey.c
+++ b/drivers/usb/misc/chaoskey.c
@@ -232,10 +232,10 @@ static void chaoskey_disconnect(struct usb_interface *interface)
 	if (dev->hwrng_registered)
 		hwrng_unregister(&dev->hwrng);
 
-	mutex_lock(&chaoskey_list_lock);
 	usb_deregister_dev(interface, &chaoskey_class);
 
 	usb_set_intfdata(interface, NULL);
+	mutex_lock(&chaoskey_list_lock);
 	mutex_lock(&dev->lock);
 
 	dev->present = false;
@@ -319,7 +319,7 @@ static int chaoskey_release(struct inode *inode, struct file *file)
 bail:
 	mutex_unlock(&dev->lock);
 destruction:
-	mutex_lock(&chaoskey_list_lock);
+	mutex_unlock(&chaoskey_list_lock);
 	usb_dbg(interface, "release success");
 	return rv;
 }