atm: iphase: fix possible use-after-free in ia_module_exit()

stable inclusion
from stable-v4.19.198
commit 89ce0b0747f319eb70f85bc820dcc43cebbd5417
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4E8
CVE: CVE-2021-47357

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=89ce0b0747f319eb70f85bc820dcc43cebbd5417



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[ Upstream commit 1c72e6ab ]

This module's remove path calls del_timer(). However, that function
does not wait until the timer handler finishes. This means that the
timer handler may still be running after the driver's remove function
has finished, which would result in a use-after-free.

Fix by calling del_timer_sync(), which makes sure the timer handler
has finished, and unable to re-schedule itself.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Liu Shixin <liushixin2@huawei.com>