This is a note to let you know that I've just added the patch titled tty: n_gsm: fix sleep-in-atomic-context bug in gsm_control_send to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: tty-n_gsm-fix-sleep-in-atomic-context-bug-in-gsm_con.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1e8ac41a8b614d7f9711efeb04018aed590e7664 Author: Duoming Zhou <duoming@xxxxxxxxxx> Date: Sun Oct 2 12:07:09 2022 +0800 tty: n_gsm: fix sleep-in-atomic-context bug in gsm_control_send [ Upstream commit 7b7dfe4833c70a11cdfa51b38705103bd31eddaa ] The function gsm_dlci_t1() is a timer handler that runs in an atomic context, but it calls "kzalloc(..., GFP_KERNEL)" that may sleep. As a result, the sleep-in-atomic-context bug will happen. The process is shown below: gsm_dlci_t1() gsm_dlci_open() gsm_modem_update() gsm_modem_upd_via_msc() gsm_control_send() kzalloc(sizeof(.., GFP_KERNEL) //may sleep This patch changes the gfp_t parameter of kzalloc() from GFP_KERNEL to GFP_ATOMIC in order to mitigate the bug. Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx> Link: https://lore.kernel.org/r/20221002040709.27849-1-duoming@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 1d50f3ab4e5a..97f6860c911e 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1425,7 +1425,7 @@ static struct gsm_control *gsm_control_send(struct gsm_mux *gsm, unsigned int command, u8 *data, int clen) { struct gsm_control *ctrl = kzalloc(sizeof(struct gsm_control), - GFP_KERNEL); + GFP_ATOMIC); unsigned long flags; if (ctrl == NULL) return NULL;