tty: n_gsm: fix sleep-in-atomic-context bug in gsm_control_send

stable inclusion
from stable-v5.10.156
commit b8fe1a5aa7330590b9bc3a57d43f488711e14955
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MCG1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b8fe1a5aa7330590b9bc3a57d43f488711e14955



--------------------------------

[ Upstream commit 7b7dfe48 ]

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: e1eaea46 ("tty: n_gsm line discipline")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20221002040709.27849-1-duoming@zju.edu.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>