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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,
        =?UTF-8?q?Jos=C3=A9=20Exp=C3=B3sito?= <jose.exposito89@gmail.com>,
        Jiri Kosina <jkosina@suse.cz>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 328/846] HID: hid-uclogic-params: Invalid parameter check in uclogic_params_init
Date:   Mon, 24 Jan 2022 19:37:25 +0100
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From: José Expósito <jose.exposito89@gmail.com>

[ Upstream commit f364c571a5c77e96de2d32062ff019d6b8d2e2bc ]

The function performs a check on its input parameters, however, the
hdev parameter is used before the check.

Initialize the stack variables after checking the input parameters to
avoid a possible NULL pointer dereference.

Fixes: 9614219e9310e ("HID: uclogic: Extract tablet parameter discovery into a module")
Addresses-Coverity-ID: 1443831 ("Null pointer dereference")
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hid/hid-uclogic-params.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-uclogic-params.c b/drivers/hid/hid-uclogic-params.c
index adff1bd68d9f8..3c10b858cf74c 100644
--- a/drivers/hid/hid-uclogic-params.c
+++ b/drivers/hid/hid-uclogic-params.c
@@ -834,10 +834,10 @@ int uclogic_params_init(struct uclogic_params *params,
 			struct hid_device *hdev)
 {
 	int rc;
-	struct usb_device *udev = hid_to_usb_dev(hdev);
-	__u8  bNumInterfaces = udev->config->desc.bNumInterfaces;
-	struct usb_interface *iface = to_usb_interface(hdev->dev.parent);
-	__u8 bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
+	struct usb_device *udev;
+	__u8  bNumInterfaces;
+	struct usb_interface *iface;
+	__u8 bInterfaceNumber;
 	bool found;
 	/* The resulting parameters (noop) */
 	struct uclogic_params p = {0, };
@@ -848,6 +848,11 @@ int uclogic_params_init(struct uclogic_params *params,
 		goto cleanup;
 	}
 
+	udev = hid_to_usb_dev(hdev);
+	bNumInterfaces = udev->config->desc.bNumInterfaces;
+	iface = to_usb_interface(hdev->dev.parent);
+	bInterfaceNumber = iface->cur_altsetting->desc.bInterfaceNumber;
+
 	/*
 	 * Set replacement report descriptor if the original matches the
 	 * specified size. Otherwise keep interface unchanged.
-- 
2.34.1