linux-kernel - [PATCH -next] mISDN: fix possible use-after-free in HFC

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Message-ID: <1620716333-108153-1-git-send-email-zou_wei@huawei.com>
Date:   Tue, 11 May 2021 14:58:53 +0800
From:   Zou Wei <zou_wei@...wei.com>
To:     <isdn@...ux-pingi.de>, <davem@...emloft.net>,
        <gustavoars@...nel.org>, <christophe.jaillet@...adoo.fr>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Zou Wei <zou_wei@...wei.com>
Subject: [PATCH -next] mISDN: fix possible use-after-free in HFC_cleanup()

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@...wei.com>
Signed-off-by: Zou Wei <zou_wei@...wei.com>
---
 drivers/isdn/hardware/mISDN/hfcpci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c
index 56bd2e9..e501cb0 100644
--- a/drivers/isdn/hardware/mISDN/hfcpci.c
+++ b/drivers/isdn/hardware/mISDN/hfcpci.c
@@ -2342,7 +2342,7 @@ 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);
 }
-- 
2.6.2