linux-kernel - [PATCH 4.4 044/149] atm: fix atm_dev refcnt leaks in atmtcp_remove

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Date:   Thu, 20 Aug 2020 11:22:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xin Xiong <xiongx18@...an.edu.cn>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 044/149] atm: fix atm_dev refcnt leaks in atmtcp_remove_persistent

From: Xin Xiong <xiongx18@...an.edu.cn>

[ Upstream commit 51875dad43b44241b46a569493f1e4bfa0386d86 ]

atmtcp_remove_persistent() invokes atm_dev_lookup(), which returns a
reference of atm_dev with increased refcount or NULL if fails.

The refcount leaks issues occur in two error handling paths. If
dev_data->persist is zero or PRIV(dev)->vcc isn't NULL, the function
returns 0 without decreasing the refcount kept by a local variable,
resulting in refcount leaks.

Fix the issue by adding atm_dev_put() before returning 0 both when
dev_data->persist is zero or PRIV(dev)->vcc isn't NULL.

Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/atm/atmtcp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/atm/atmtcp.c b/drivers/atm/atmtcp.c
index 480fa6ffbc090..04fca6db273ef 100644
--- a/drivers/atm/atmtcp.c
+++ b/drivers/atm/atmtcp.c
@@ -432,9 +432,15 @@ static int atmtcp_remove_persistent(int itf)
 		return -EMEDIUMTYPE;
 	}
 	dev_data = PRIV(dev);
-	if (!dev_data->persist) return 0;
+	if (!dev_data->persist) {
+		atm_dev_put(dev);
+		return 0;
+	}
 	dev_data->persist = 0;
-	if (PRIV(dev)->vcc) return 0;
+	if (PRIV(dev)->vcc) {
+		atm_dev_put(dev);
+		return 0;
+	}
 	kfree(dev_data);
 	atm_dev_put(dev);
 	atm_dev_deregister(dev);
-- 
2.25.1