linux-kernel - Re: [PATCH] tty: fix data race in n_tty_receive_buf

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Message-ID: <736cab12-44c3-9bd1-168e-901ef907de74@codeaurora.org>
Date:   Wed, 17 Jan 2018 18:55:50 +0530
From:   "Kohli, Gaurav" <gkohli@...eaurora.org>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
Cc:     jslaby@...e.com, gregkh@...uxfoundation.org, mikey@...ling.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] tty: fix data race in n_tty_receive_buf_common

On 1/6/2018 1:20 PM, Kohli, Gaurav wrote:

> On 1/6/2018 2:35 AM, Alan Cox wrote:
>> On Sat, 6 Jan 2018 01:54:36 +0530
>> "Kohli, Gaurav" <gkohli@...eaurora.org> wrote:
>>> Hi Alan,
>>> Sorry correcting the typo here:
>>> +retval =  tty_ldisc_lock(tty, 5 * HZ);
>>> +if (retval)
>>> +         goto err_release_lock;
>>> tty->port->itty = tty;
>>> /*
>>> * Structures all installed ... call the ldisc open routines.
>>> * If we fail here just call release_tty to clean up.  No need
>>> * to decrement the use counts, as release_tty doesn't care.
>>> */
>>> retval = tty_ldisc_setup(tty, tty->link);
>>>            if (retval)
>>>                goto err_release_tty;
>>> tty_ldisc_unlock(tty);
>>> err_release_tty:
>>> tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
>>>        retval, idx);
>>> +err_release_lock;
>>> +tty_unlock(tty);
>>> +release_tty(tty, idx);
>>> +tty_ldisc_unlock(tty);
>>> +return ERR_PTR(retval);
>> Thanks - can you give that a testing since for some reason you seem to be
>> the only system able to hit this and confirm that it's now working
>> properly. Then I'll push it upstream
>> And thanks for doing all the debug work to find this and identify what
>> was going on.
>> Alan
>> --
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> Thanks Alan for your support, yes we will try to reproduce and get back
> to you.
> Ideally it take 2-3 days for issue reproduction, but yes it is
> consistently reproducible.
> Regards
> Gaurav

Hi Alan,
Sorry for the delayed response, as i was waiting for test results.
I have uploaded the new patch v1 as per your suggestions and result 
looks good.

Thanks
Gaurav
>
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