The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

4bb1a53be85f ("tty: n_gsm: initialize more members at gsm_alloc_mux()") 734966043860 ("tty: n_gsm: fix resource allocation order in gsm_activate_mux()") 0af021678d5d ("tty: n_gsm: fix deadlock and link starvation in outgoing data path") bec0224816d1 ("tty: n_gsm: fix non flow control frames during mux flow off") c568f7086c6e ("tty: n_gsm: fix missing timer to handle stalled links") 556fc8ac0651 ("tty: n_gsm: fix wrong queuing behavior in gsm_dlci_data_output()") 01aecd917114 ("tty: n_gsm: fix tty registration before control channel open") 925ea0fa5277 ("tty: n_gsm: Fix packet data hex dump output") f4f7d6328721 ("tty: n_gsm: fix software flow control handling") c19ffe00fed6 ("tty: n_gsm: fix invalid use of MSC in advanced option") a8c5b8255f8a ("tty: n_gsm: fix broken virtual tty handling") 48473802506d ("tty: n_gsm: fix missing update of modem controls after DLCI open") 73029a4d7161 ("tty: n_gsm: fix reset fifo race condition") 398867f59f95 ("tty: n_gsm: fix wrong command frame length field encoding") 17eac6520285 ("tty: n_gsm: fix missing explicit ldisc flush") deefc58bafb4 ("tty: n_gsm: fix wrong DLCI release order") 7a0e4b1733b6 ("tty: n_gsm: fix frame reception handling") 06d5afd4d640 ("tty: n_gsm: fix wrong signal octet encoding in convergence layer type 2") 284260f278b7 ("tty: n_gsm: fix mux cleanup after unregister tty device") 1ec92e974277 ("tty: n_gsm: fix decoupled mux resource")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4bb1a53be85fcb1e24c14860e326a00cdd362c28 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Date: Sat, 27 Aug 2022 22:47:19 +0900 Subject: [PATCH] tty: n_gsm: initialize more members at gsm_alloc_mux()

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().

Link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12 [1] Fixes: 32dd59f96924f45e ("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: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 38688cb16c20..d6598ca3640f 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; @@ -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; }