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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hulk Robot <hulkci@huawei.com>,
        Zou Wei <zou_wei@huawei.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 126/245] atm: iphase: fix possible use-after-free in ia_module_exit()
Date:   Mon, 19 Jul 2021 16:51:08 +0200
Message-Id: <20210719144944.484301189@linuxfoundation.org>
In-Reply-To: <20210719144940.288257948@linuxfoundation.org>
References: <20210719144940.288257948@linuxfoundation.org>
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From: Zou Wei <zou_wei@huawei.com>

[ Upstream commit 1c72e6ab66b9598cac741ed397438a52065a8f1f ]

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/iphase.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/atm/iphase.c b/drivers/atm/iphase.c
index fe47c924dc64..a1427cb9b9ed 100644
--- a/drivers/atm/iphase.c
+++ b/drivers/atm/iphase.c
@@ -3301,7 +3301,7 @@ static void __exit ia_module_exit(void)
 {
 	pci_unregister_driver(&ia_driver);
 
-        del_timer(&ia_timer);
+	del_timer_sync(&ia_timer);
 }
 
 module_init(ia_module_init);
-- 
2.30.2