linux-kernel - Re: Semi-typical watchdog bug re early misc

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Message-ID: <20070326203017.GA4014@infomag.infomag.iguana.be>
Date:	Mon, 26 Mar 2007 22:30:17 +0200
From:	Wim Van Sebroeck <wim@...ana.be>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Semi-typical watchdog bug re early misc_register()

Hi Alexey,

> It seems that some watchdog drivers are doing following mistake:
> 
> 	rv = misc_register();
> 	if (rv < 0)
> 		return rv;
> 	rv = request_region();
> 	if (rv < 0) {
> 		misc_deregister();
> 		return rv;
> 	}
> 
> But, right after misc_register() returns, misc device can be opened and
> ioctls interacting with hardware issued, and driver can do outb() to
> port it doesn't own yet, because request_region() is still pending.

Totally agree. patch has been added to linux-2.6-watchdog-mm tree.

> Also, is there similar ordering between register_reboot_notifier() and
> misc_register() ? Some drivers do misc_register() last, some register
> reboot notifiers.

I prefer that the reboot notifiers are loaded before you give userspace the
ability to communicate with the driver.

Greetings,
Wim.

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