From: Dmitry Safonov <dima@arista.com>
To: Jiri Slaby <jslaby@suse.cz>, linux-kernel@vger.kernel.org
Cc: "Daniel Axtens" <dja@axtens.net>,
"Dmitry Safonov" <0x7f454c46@gmail.com>,
"Sergey Senozhatsky" <sergey.senozhatsky.work@gmail.com>,
"Dmitry Vyukov" <dvyukov@google.com>,
"Tan Xiaojun" <tanxiaojun@huawei.com>,
"Peter Hurley" <peter@hurleysoftware.com>,
"Pasi Kärkkäinen" <pasik@iki.fi>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Michael Neuling" <mikey@neuling.org>,
"Mikulas Patocka" <mpatocka@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/4] tty: Drop tty->count on tty_reopen() failure
Date: Wed, 29 Aug 2018 17:13:27 +0100 [thread overview]
Message-ID: <1535559207.23560.55.camel@arista.com> (raw)
In-Reply-To: <cbedde00-a0f4-6714-f7f4-a180dca15ce0@suse.cz>
On Wed, 2018-08-29 at 16:38 +0200, Jiri Slaby wrote:
> On 08/29/2018, 04:23 AM, Dmitry Safonov wrote:
> > In case of tty_ldisc_reinit() failure, tty->count should be
> > decremented
> > back, otherwise we will never release_tty().
> > Never seen it in the real life, but it seems not really hard to
> > hit.
>
> I did see it. And this fixes it.
Thanks, I'll add your tested-by, if I'll have to resend.
>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Jiri Slaby <jslaby@suse.com>
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Dmitry Safonov <dima@arista.com>
> > ---
> > drivers/tty/tty_io.c | 11 ++++++++---
> > 1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> > index 32bc3e3fe4d3..5e5da9acaf0a 100644
> > --- a/drivers/tty/tty_io.c
> > +++ b/drivers/tty/tty_io.c
> > @@ -1255,6 +1255,7 @@ static void tty_driver_remove_tty(struct
> > tty_driver *driver, struct tty_struct *
> > static int tty_reopen(struct tty_struct *tty)
> > {
> > struct tty_driver *driver = tty->driver;
> > + int retval;
> >
> > if (driver->type == TTY_DRIVER_TYPE_PTY &&
> > driver->subtype == PTY_TYPE_MASTER)
> > @@ -1268,10 +1269,14 @@ static int tty_reopen(struct tty_struct
> > *tty)
> >
> > tty->count++;
> >
> > - if (!tty->ldisc)
> > - return tty_ldisc_reinit(tty, tty->termios.c_line);
> > + if (tty->ldisc)
> > + return 0;
> >
> > - return 0;
> > + retval = tty_ldisc_reinit(tty, tty->termios.c_line);
> > + if (retval)
> > + tty->count--;
>
> I would just do:
> if (!retval)
> tty->count++;
> here. Nobody from ldiscs should rely on tty->count.
I thought about that and probably should have described in commit
message why I haven't done that: I prefer to keep it as was as I did Cc
stable tree - to keep the chance of regression to minimum.
I agree that your way is cleaner, but probably it may be done as
cleanup on top for linux-next..
--
Thanks,
Dmitry
next prev parent reply other threads:[~2018-08-29 16:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-29 2:23 [PATCH 0/4] tty: Hold write ldisc sem in tty_reopen() Dmitry Safonov
2018-08-29 2:23 ` [PATCH 1/4] tty: Drop tty->count on tty_reopen() failure Dmitry Safonov
2018-08-29 14:38 ` Jiri Slaby
2018-08-29 16:13 ` Dmitry Safonov [this message]
2018-08-31 6:47 ` Jiri Slaby
2018-08-31 11:54 ` Dmitry Safonov
2018-08-29 2:23 ` [PATCH 2/4] tty: Hold tty_ldisc_lock() during tty_reopen() Dmitry Safonov
2018-08-29 4:34 ` Sergey Senozhatsky
2018-08-29 14:30 ` Dmitry Safonov
2018-08-30 5:16 ` Benjamin Herrenschmidt
2018-08-29 14:40 ` Jiri Slaby
2018-08-29 14:45 ` Jiri Slaby
2018-08-29 16:36 ` Dmitry Safonov
2018-08-29 15:19 ` Tetsuo Handa
2018-08-31 6:51 ` Jiri Slaby
2018-08-31 11:17 ` Tetsuo Handa
2018-08-31 11:21 ` Jiri Slaby
2018-08-31 12:12 ` Dmitry Safonov
2018-09-07 4:50 ` [LKP] [tty] 0b4f83d510: INFO:task_blocked_for_more_than#seconds kernel test robot
2018-09-07 6:39 ` Jiri Slaby
2018-09-07 11:12 ` Dmitry Safonov
2018-09-10 5:14 ` Sergey Senozhatsky
2018-09-10 18:50 ` Dmitry Safonov
2018-08-29 2:23 ` [PATCH 3/4] tty: Lock tty pair in tty_init_dev() Dmitry Safonov
2018-08-29 14:46 ` Jiri Slaby
2018-08-29 16:28 ` Dmitry Safonov
2018-08-31 6:54 ` Jiri Slaby
2018-08-31 12:22 ` Dmitry Safonov
2018-08-29 2:23 ` [PATCH 4/4] tty/lockdep: Add ldisc_sem asserts Dmitry Safonov
2018-08-30 7:03 ` [PATCH 0/4] tty: Hold write ldisc sem in tty_reopen() Pasi Kärkkäinen
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