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

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Date:   Fri, 5 Jan 2018 21:05:29 +0000
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     "Kohli, Gaurav" <gkohli@...eaurora.org>
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 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