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([2a0b:e7c0:0:107::70f]) by smtp.gmail.com with ESMTPSA id ku13-20020a170907788d00b00728f6d4d0d7sm4109174ejc.67.2022.08.29.00.10.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Aug 2022 00:10:04 -0700 (PDT) Message-ID: <89830d6e-fe70-eb68-84fe-1b60657ac3d8@kernel.org> Date: Mon, 29 Aug 2022 09:10:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH] tty: n_gsm: initialize more members at gsm_alloc_mux() Content-Language: en-US To: Tetsuo Handa , Daniel Starke Cc: syzbot , gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <0000000000008be58e05e5b5d971@google.com> <000000000000434f7a05e5bab1ce@google.com> <2110618e-57f0-c1ce-b2ad-b6cacef3f60e@I-love.SAKURA.ne.jp> From: Jiri Slaby In-Reply-To: <2110618e-57f0-c1ce-b2ad-b6cacef3f60e@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27. 08. 22, 15:47, Tetsuo Handa wrote: > syzbot is reporting use of uninitialized spinlock at gsmld_write() [1], for > commit 32dd59f96924f45e ("tty: n_gsm: fix race condition in gsmld_write()") > allows accessing gsm->tx_lock before gsm_activate_mux() initializes it. > > Since object initialization should be done right after allocation in order > to avoid accessing uninitialized memory, move initialization of > timer/work/waitqueue/spinlock from gsmld_open()/gsm_activate_mux() to > gsm_alloc_mux(). LGTM, I wonder why this was not like this forever. Acked-by: Jiri Slaby > Link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12 [1] > Reported-by: syzbot > Signed-off-by: Tetsuo Handa > Tested-by: syzbot > Fixes: 32dd59f96924f45e ("tty: n_gsm: fix race condition in gsmld_write()") > --- > drivers/tty/n_gsm.c | 17 ++++++----------- > 1 file changed, 6 insertions(+), 11 deletions(-) > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > index caa5c14ed57f..70cd90474679 100644 > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -2501,13 +2501,6 @@ static int gsm_activate_mux(struct gsm_mux *gsm) > if (dlci == NULL) > return -ENOMEM; > > - timer_setup(&gsm->kick_timer, gsm_kick_timer, 0); > - timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); > - INIT_WORK(&gsm->tx_work, gsmld_write_task); > - init_waitqueue_head(&gsm->event); > - spin_lock_init(&gsm->control_lock); > - spin_lock_init(&gsm->tx_lock); > - > if (gsm->encoding == 0) > gsm->receive = gsm0_receive; > else > @@ -2612,6 +2605,12 @@ static struct gsm_mux *gsm_alloc_mux(void) > kref_init(&gsm->ref); > INIT_LIST_HEAD(&gsm->tx_ctrl_list); > INIT_LIST_HEAD(&gsm->tx_data_list); > + timer_setup(&gsm->kick_timer, gsm_kick_timer, 0); > + timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); > + INIT_WORK(&gsm->tx_work, gsmld_write_task); > + init_waitqueue_head(&gsm->event); > + spin_lock_init(&gsm->control_lock); > + spin_lock_init(&gsm->tx_lock); > > gsm->t1 = T1; > gsm->t2 = T2; > @@ -2946,10 +2945,6 @@ static int gsmld_open(struct tty_struct *tty) > > gsmld_attach_gsm(tty, gsm); > > - timer_setup(&gsm->kick_timer, gsm_kick_timer, 0); > - timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); > - INIT_WORK(&gsm->tx_work, gsmld_write_task); > - > return 0; > } > -- js suse labs