linux-kernel - Re: [syzbot] [kernel?] WARNING in driver

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Message-ID: <20250705081850.2552-1-hdanton@sina.com>
Date: Sat,  5 Jul 2025 16:18:49 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+6616bba359cec7a1def1@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [kernel?] WARNING in driver_unregister (2)

> Date: Fri, 04 Jul 2025 20:20:34 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    c435a4f487e8 Merge tag 'riscv-for-linus-6.16-rc5' of git:/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=138f8f70580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5ba6cef8f153bfeb
> dashboard link: https://syzkaller.appspot.com/bug?extid=6616bba359cec7a1def1
> 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=10b8febc580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=118f6c8c580000

#syz test

--- x/drivers/comedi/drivers.c
+++ y/drivers/comedi/drivers.c
@@ -994,10 +994,13 @@ int comedi_device_attach(struct comedi_d
 	dev->board_name = dev->board_ptr ? *(const char **)dev->board_ptr
 					 : dev->driver->driver_name;
 	ret = driv->attach(dev, it);
-	if (ret >= 0)
+	if (ret >= 0) {
 		ret = comedi_device_postconfig(dev);
-	if (ret < 0) {
-		comedi_device_detach(dev);
+		if (ret < 0) {
+			comedi_device_detach(dev);
+			module_put(driv->module);
+		}
+	} else {
 		module_put(driv->module);
 	}
 	/* On success, the driver module count has been incremented. */
--