linux-kernel - [PATCH AUTOSEL 5.4 099/266] staging: gasket: Fix mapping refcnt leak when put attribute fails

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Message-Id: <20200618011631.604574-99-sashal@kernel.org>
Date:   Wed, 17 Jun 2020 21:13:44 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, devel@...verdev.osuosl.org
Subject: [PATCH AUTOSEL 5.4 099/266] staging: gasket: Fix mapping refcnt leak when put attribute fails

From: Xiyu Yang <xiyuyang19@...an.edu.cn>

[ Upstream commit 57a66838e1494cd881b7f4e110ec685736e8e3ca ]

gasket_sysfs_put_attr() invokes get_mapping(), which returns a reference
of the specified gasket_sysfs_mapping object to "mapping" with increased
refcnt.

When gasket_sysfs_put_attr() returns, local variable "mapping" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one path of
gasket_sysfs_put_attr(). When mapping attribute is unknown, the function
forgets to decrease the refcnt increased by get_mapping(), causing a
refcnt leak.

Fix this issue by calling put_mapping() when put attribute fails due to
unknown attribute.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Link: https://lore.kernel.org/r/1587618895-13660-1-git-send-email-xiyuyang19@fudan.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/staging/gasket/gasket_sysfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/staging/gasket/gasket_sysfs.c b/drivers/staging/gasket/gasket_sysfs.c
index 5f0e089573a2..ad852ea1d4a9 100644
--- a/drivers/staging/gasket/gasket_sysfs.c
+++ b/drivers/staging/gasket/gasket_sysfs.c
@@ -339,6 +339,7 @@ void gasket_sysfs_put_attr(struct device *device,
 
 	dev_err(device, "Unable to put unknown attribute: %s\n",
 		attr->attr.attr.name);
+	put_mapping(mapping);
 }
 EXPORT_SYMBOL(gasket_sysfs_put_attr);
 
-- 
2.25.1