linux-kernel - [PATCH 5.4 098/314] staging: gasket: Fix mapping refcnt leak when register/store fails

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Date:   Tue, 23 Jun 2020 21:54:53 +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, Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 098/314] staging: gasket: Fix mapping refcnt leak when register/store fails

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

[ Upstream commit e3436ce60cf5f5eaedda2b8c622f69feb97595e2 ]

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

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

The reference counting issue happens in one exception handling path of
gasket_sysfs_register_store(). When gasket_dev is NULL, the function
forgets to decrease the refcnt increased by get_mapping(), causing a
refcnt leak.

Fix this issue by calling put_mapping() when gasket_dev is NULL.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Link: https://lore.kernel.org/r/1587618941-13718-1-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 ad852ea1d4a92..af26bc9f184a5 100644
--- a/drivers/staging/gasket/gasket_sysfs.c
+++ b/drivers/staging/gasket/gasket_sysfs.c
@@ -373,6 +373,7 @@ ssize_t gasket_sysfs_register_store(struct device *device,
 	gasket_dev = mapping->gasket_dev;
 	if (!gasket_dev) {
 		dev_err(device, "Device driver may have been removed\n");
+		put_mapping(mapping);
 		return 0;
 	}
 
-- 
2.25.1