Commit 4bb1a53b authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Greg Kroah-Hartman
Browse files

tty: n_gsm: initialize more members at gsm_alloc_mux() 

syzbot is reporting use of uninitialized spinlock at gsmld_write() [1], for
commit 32dd59f9 ("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().

Link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12

 [1]
Fixes: 32dd59f9 ("tty: n_gsm: fix race condition in gsmld_write()")
Reported-by: default avatarsyzbot <syzbot+cf155def4e717db68a12@syzkaller.appspotmail.com>
Tested-by: default avatarsyzbot <syzbot+cf155def4e717db68a12@syzkaller.appspotmail.com>
Cc: stable <stable@kernel.org>
Acked-by: default avatarJiri Slaby <jirislaby@kernel.org>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://lore.kernel.org/r/2110618e-57f0-c1ce-b2ad-b6cacef3f60e@I-love.SAKURA.ne.jp


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f16c6d2e

drivers/tty/n_gsm.c

+6 −11
Original line number Diff line number Diff line
@@ -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;
@@ -2947,10 +2946,6 @@ 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;

}