linux-kernel - Re: [PATCH] fix unchecked mutex_lock_interruptible (was Re: use mutex instead of semaphore in RocketPort driver)

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Message-ID: <20070523135911.GC31790@traven>
Date:	Wed, 23 May 2007 15:59:11 +0200
From:	Matthias Kaehlcke <matthias.kaehlcke@...il.com>
To:	Satyam Sharma <satyam.sharma@...il.com>
Cc:	Jiri Slaby <jirislaby@...il.com>, Simon Arlott <simon@...e.lp0.eu>,
	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] fix unchecked mutex_lock_interruptible (was Re: use mutex instead of semaphore in RocketPort driver)

El Wed, May 23, 2007 at 06:25:49PM +0530 Satyam Sharma ha dit:

> On 5/23/07, Jiri Slaby <jirislaby@...il.com> wrote:
> >Simon Arlott napsal(a):
> >> On 22/05/07 21:06, Matthias Kaehlcke wrote:
> >>> would the following resolve the problem?
> >>>
> >>> if(mutex_lock_interruptible(&info->write_mtx))         return
> >>> -ERESTARTSYS
> >>>
> >>> thanks for your comments
> 
> Hum. I remember suggesting the fix when this came few weeks back,
> somehow the older version seems to have made it into Linus' tree.

i also remembered your suggestion but thought it was a similar case in
another driver. i think it's my fault that the older version made it
into the Linus tree cause i sent the patch in a new thread instead of
responding to the initial post :(
 
> >> No. At least one user of tty_operations/tty_driver's write function
> >> doesn't check the return value so it would never be retried, mutex_lock
> >> should be used instead.
> 
> Replacing mutex_lock_interruptible() with a mutex_lock() could be a
> change in behaviour visible to userspace. Best to continue to use
> _interruptible. Returning EINTR would be safe choice because if
> Simon's right that this isn't retried, we could end up breaking
> userspace that isn't quite ready to see ERESTARTSYS coming out of
> a write(2), but ...

thanks for your fix!

-- 
Matthias Kaehlcke
Linux Application Developer
Barcelona

       The yellow ships hung in the air just like bricks dont do
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