[PATCH 5.16 094/285] can: etas_es58x: es58x_fd_rx_event_msg(): initialize rx_event_msg before calling es58x_check_msg_len()

Greg Kroah-Hartman
2022-04-12T07:45:52Z

From: Vincent Mailhol <mailhol.vincent@wanadoo.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@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.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 4f0cae29f4d8..b71d1530638b 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));
--
2.35.1