linux-kernel - Re: [PATCH] drivers: isdn: capi: Fix data-race bug

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Date:   Fri, 24 Jul 2020 10:18:07 +0530
From:   Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     madhuparnabhowmik10@...il.com, isdn@...ux-pingi.de, arnd@...db.de,
        gregkh@...uxfoundation.org, edumazet@...gle.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        andrianov@...ras.ru, ldv-project@...uxtesting.org
Subject: Re: [PATCH] drivers: isdn: capi: Fix data-race bug

On Thu, Jul 23, 2020 at 03:11:58PM -0700, David Miller wrote:
> From: madhuparnabhowmik10@...il.com
> Date: Wed, 22 Jul 2020 22:53:29 +0530
> 
> > From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> > 
> > In capi_init(), after register_chrdev() the file operation callbacks
> > can be called. However capinc_tty_init() is called later.
> > Since capiminors and capinc_tty_driver are initialized in
> > capinc_tty_init(), their initialization can race with their usage
> > in various callbacks like in capi_release().
> > 
> > Therefore, call capinc_tty_init() before register_chrdev to avoid
> > such race conditions.
> > 
> > Found by Linux Driver Verification project (linuxtesting.org).
> > 
> > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> 
> I agree with Arnd that this just exchanges one set of problems for
> another.

Thanks Arnd and David, for reviewing the patch.
Do you have any suggestions on how to fix this correctly?

Regards,
Madhuparna