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

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Message-Id: <20200723.151158.2190104866687627036.davem@davemloft.net>
Date:   Thu, 23 Jul 2020 15:11:58 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     madhuparnabhowmik10@...il.com
Cc:     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

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.