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Mon, 03 Sep 2018 18:51:42 -0700 (PDT) Date: Tue, 4 Sep 2018 10:51:39 +0900 From: Sergey Senozhatsky To: Dmitry Safonov Cc: linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Daniel Axtens , Dmitry Vyukov , Michael Neuling , Mikulas Patocka , Nathan March , Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= , Peter Hurley , Sergey Senozhatsky , Tan Xiaojun , Tetsuo Handa , syzbot+3aa9784721dfb90e984d@syzkaller.appspotmail.com, Greg Kroah-Hartman , Jiri Slaby , stable@vger.kernel.org Subject: Re: [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen() Message-ID: <20180904015139.GA4251@jagdpanzerIV> References: <20180903165257.29227-1-dima@arista.com> <20180903165257.29227-3-dima@arista.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180903165257.29227-3-dima@arista.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (09/03/18 17:52), Dmitry Safonov wrote: > > We've seen the following crash on v4.9.108 stable: > > BUG: unable to handle kernel paging request at 0000000000002260 > IP: [..] n_tty_receive_buf_common+0x5f/0x86d > Workqueue: events_unbound flush_to_ldisc > Call Trace: > [..] n_tty_receive_buf2 > [..] tty_ldisc_receive_buf > [..] flush_to_ldisc > [..] process_one_work > [..] worker_thread > [..] kthread > [..] ret_from_fork > > tty_ldisc_reinit() should be called with ldisc_sem hold for writing, > which will protect any reader against line discipline changes. > > Cc: Greg Kroah-Hartman > Cc: Jiri Slaby > Cc: stable@vger.kernel.org # depends on commit b027e2298bd5 ("tty: fix > data race between tty_init_dev and flush of buf") I believe there's a "Fixes" tag for that Fixes: b027e2298bd5 ("tty: fix data race between tty_init_dev and flush of buf") Cc: stable@vger.kernel.org -ss