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From: Greg KH <gregkh@linuxfoundation.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: jslaby@suse.com,
	syzbot <syzbot+3aa9784721dfb90e984d@syzkaller.appspotmail.com>,
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2] n_tty: Protect tty->disc_data using refcount.
Date: Wed, 25 Jul 2018 10:06:30 +0200	[thread overview]
Message-ID: <20180725080630.GA17932@kroah.com> (raw)
In-Reply-To: <8e83cd9a-e28c-a9f4-5f47-98f2046a5dfb@I-love.SAKURA.ne.jp>

On Wed, Jul 25, 2018 at 12:22:16AM +0900, Tetsuo Handa wrote:
> >From 118c64e86641a97d44dec39e313a95b12d9bc3b2 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Date: Wed, 25 Jul 2018 00:15:18 +0900
> Subject: [PATCH v2] n_tty: Protect tty->disc_data using refcount.
> 
> syzbot is reporting NULL pointer dereference at n_tty_set_termios() [1].
> This is because ioctl(TIOCVHANGUP) versus ioctl(TCSETS) can race.
> 
> Since we don't want to introduce new locking dependency, this patch
> converts "struct n_tty_data *ldata = tty->disc_data;" in individual
> function into a function argument which follows "struct tty *", and
> holds tty->disc_data at each "struct tty_ldisc_ops" hook using refcount
> in order to ensure that memory which contains "struct n_tty_data" will
> not be released while processing individual function.
> 
> [1] https://syzkaller.appspot.com/bug?id=1e850009fca0b64ce49dc16499bda4f7de0ab1a5
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
>  drivers/tty/n_tty.c | 511 ++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 314 insertions(+), 197 deletions(-)

What changed from v1?  I haven't had the chance to review your first
patch, sorry, it's still in my queue.  I was hoping that someone else
would help out with that as well :)

thanks,

greg k-h

  reply	other threads:[~2018-07-25  8:06 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <001a113ed31a122ced0568cc6be1@google.com>
     [not found] ` <db45a090-593d-23d2-e6b2-ede5b308f02f@I-love.SAKURA.ne.jp>
     [not found]   ` <35d649ce-0c22-f839-aa4d-19733bf31a9c@I-love.SAKURA.ne.jp>
2018-07-17 10:14     ` [PATCH] n_tty: Protect tty->disc_data using refcount Tetsuo Handa
2018-07-24 15:22       ` [PATCH v2] " Tetsuo Handa
2018-07-25  8:06         ` Greg KH [this message]
2018-07-25 12:35           ` Tetsuo Handa
2018-08-29 13:53         ` Jiri Slaby
2018-08-29 14:48           ` Jiri Slaby
2018-08-29 15:02           ` Tetsuo Handa

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