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From:   Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Date:   Fri, 24 Jul 2020 20:28:35 +0530
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
        David Miller <davem@davemloft.net>, isdn@linux-pingi.de,
        arnd@arndb.de, edumazet@google.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, andrianov@ispras.ru,
        ldv-project@linuxtesting.org
Subject: Re: [PATCH] drivers: isdn: capi: Fix data-race bug
Message-ID: <20200724145835.GA30994@madhuparna-HP-Notebook>
References: <20200722172329.16727-1-madhuparnabhowmik10@gmail.com>
 <20200723.151158.2190104866687627036.davem@davemloft.net>
 <20200724044807.GA474@madhuparna-HP-Notebook>
 <20200724065747.GF3880088@kroah.com>
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On Fri, Jul 24, 2020 at 08:57:47AM +0200, Greg KH wrote:
> On Fri, Jul 24, 2020 at 10:18:07AM +0530, Madhuparna Bhowmik wrote:
> > On Thu, Jul 23, 2020 at 03:11:58PM -0700, David Miller wrote:
> > > From: madhuparnabhowmik10@gmail.com
> > > Date: Wed, 22 Jul 2020 22:53:29 +0530
> > > 
> > > > From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.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@gmail.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?
> 
> Based on the installed base of ISDN systems, and the fact that no one
> has ever actually hit this race and reported it ever, I wouldn't worry
> about it :)
>
Fair enough! Thanks for having a look.

Regards,
Madhuparna

> thanks,
> 
> greg k-h