From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
commit 4bb1a53be85fcb1e24c14860e326a00cdd362c28 upstream.
syzbot is reporting use of uninitialized spinlock at gsmld_write() [1], for commit 32dd59f ("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: 32dd59f ("tty: n_gsm: fix race condition in gsmld_write()") Reported-by: syzbot syzbot+cf155def4e717db68a12@syzkaller.appspotmail.com Tested-by: syzbot syzbot+cf155def4e717db68a12@syzkaller.appspotmail.com Cc: stable stable@kernel.org Acked-by: Jiri Slaby jirislaby@kernel.org Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Link: https://lore.kernel.org/r/2110618e-57f0-c1ce-b2ad-b6cacef3f60e@I-love.SAKURA... Signed-off-by: Fedor Pchelkin pchelkin@ispras.ru Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/n_gsm.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
--- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2200,11 +2200,6 @@ static int gsm_activate_mux(struct gsm_m { struct gsm_dlci *dlci;
- timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); - 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 @@ -2306,6 +2301,10 @@ static struct gsm_mux *gsm_alloc_mux(voi mutex_init(&gsm->mutex); kref_init(&gsm->ref); INIT_LIST_HEAD(&gsm->tx_list); + timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); + init_waitqueue_head(&gsm->event); + spin_lock_init(&gsm->control_lock); + spin_lock_init(&gsm->tx_lock);
gsm->t1 = T1; gsm->t2 = T2;