mISDN: fix possible use-after-free in HFC_cleanup()

[ Upstream commit 009fc857c5f6fda81f2f7dd851b2d54193a8e733 ]

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>

diff --git a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c
index ff48da61c94c849bf06cbb9ab9cb149515dcd626..89cf1d695a01cbc4d6d6ea0cb19b9793c2a89277 100644 (file)
--- a/drivers/isdn/hardware/mISDN/hfcpci.c
+++ b/drivers/isdn/hardware/mISDN/hfcpci.c
@@ -2352,7 +2352,7 @@ static void __exit
 HFC_cleanup(void)
 {
        if (timer_pending(&hfc_tl))
-               del_timer(&hfc_tl);
+               del_timer_sync(&hfc_tl);
 
        pci_unregister_driver(&hfc_driver);
 }