linux-kernel - [PATCH AUTOSEL 5.15 80/98] can: etas_es58x: es58x_fd_rx_event_msg(): initialize rx_event_msg before calling es58x_check_msg

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Message-Id: <20220401143742.1952163-80-sashal@kernel.org>
Date:   Fri,  1 Apr 2022 10:37:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Sasha Levin <sashal@...nel.org>, wg@...ndegger.com,
        davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 80/98] can: etas_es58x: es58x_fd_rx_event_msg(): initialize rx_event_msg before calling es58x_check_msg_len()

From: Vincent Mailhol <mailhol.vincent@...adoo.fr>

[ Upstream commit 7a8cd7c0ee823a1cc893ab3feaa23e4b602bfb9a ]

Function es58x_fd_rx_event() invokes the es58x_check_msg_len() macro:

| 	ret = es58x_check_msg_len(es58x_dev->dev, *rx_event_msg, msg_len);

While doing so, it dereferences an uninitialized
variable: *rx_event_msg.

This is actually harmless because es58x_check_msg_len() only uses
preprocessor macros (sizeof() and __stringify()) on
*rx_event_msg. c.f. [1].

Nonetheless, this pattern is confusing so the lines are reordered to
make sure that rx_event_msg is correctly initialized.

This patch also fixes a false positive warning reported by cppcheck:

| cppcheck possible warnings: (new ones prefixed by >>, may not be real problems)
|
|    In file included from drivers/net/can/usb/etas_es58x/es58x_fd.c:
| >> drivers/net/can/usb/etas_es58x/es58x_fd.c:174:8: warning: Uninitialized variable: rx_event_msg [uninitvar]
|     ret = es58x_check_msg_len(es58x_dev->dev, *rx_event_msg, msg_len);
|           ^

[1] https://elixir.bootlin.com/linux/v5.16/source/drivers/net/can/usb/etas_es58x/es58x_core.h#L467

Link: https://lore.kernel.org/all/20220306101302.708783-1-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/can/usb/etas_es58x/es58x_fd.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/can/usb/etas_es58x/es58x_fd.c b/drivers/net/can/usb/etas_es58x/es58x_fd.c
index af042aa55f59..26bf4775e884 100644
--- a/drivers/net/can/usb/etas_es58x/es58x_fd.c
+++ b/drivers/net/can/usb/etas_es58x/es58x_fd.c
@@ -171,12 +171,11 @@ static int es58x_fd_rx_event_msg(struct net_device *netdev,
 	const struct es58x_fd_rx_event_msg *rx_event_msg;
 	int ret;
 
+	rx_event_msg = &es58x_fd_urb_cmd->rx_event_msg;
 	ret = es58x_check_msg_len(es58x_dev->dev, *rx_event_msg, msg_len);
 	if (ret)
 		return ret;
 
-	rx_event_msg = &es58x_fd_urb_cmd->rx_event_msg;
-
 	return es58x_rx_err_msg(netdev, rx_event_msg->error_code,
 				rx_event_msg->event_code,
 				get_unaligned_le64(&rx_event_msg->timestamp));
-- 
2.34.1