From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 25 Jul 2018 10:06:30 +0200 From: Greg KH To: Tetsuo Handa Cc: jslaby@suse.com, syzbot , linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Alexander Viro , linux-fsdevel Subject: Re: [PATCH v2] n_tty: Protect tty->disc_data using refcount. Message-ID: <20180725080630.GA17932@kroah.com> References: <001a113ed31a122ced0568cc6be1@google.com> <35d649ce-0c22-f839-aa4d-19733bf31a9c@I-love.SAKURA.ne.jp> <83fdde07-2f8e-8d20-30a2-a8f0804a5044@I-love.SAKURA.ne.jp> <8e83cd9a-e28c-a9f4-5f47-98f2046a5dfb@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8e83cd9a-e28c-a9f4-5f47-98f2046a5dfb@I-love.SAKURA.ne.jp> Sender: linux-kernel-owner@vger.kernel.org List-ID: 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 > 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 > --- > 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