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    Subject[PATCH AUTOSEL 4.19 10/55] atm: nicstar: Fix possible use-after-free in nicstar_cleanup()
    Date
    From: Zou Wei <zou_wei@huawei.com>

    [ Upstream commit 34e7434ba4e97f4b85c1423a59b2922ba7dff2ea ]

    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>
    ---
    drivers/atm/nicstar.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/atm/nicstar.c b/drivers/atm/nicstar.c
    index 0d3754a4ac20..5281db3d6783 100644
    --- a/drivers/atm/nicstar.c
    +++ b/drivers/atm/nicstar.c
    @@ -296,7 +296,7 @@ static void __exit nicstar_cleanup(void)
    {
    XPRINTK("nicstar: nicstar_cleanup() called.\n");

    - del_timer(&ns_timer);
    + del_timer_sync(&ns_timer);

    pci_unregister_driver(&nicstar_driver);

    --
    2.30.2
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