linux-kernel - [PATCH] myri10ge: avoid uninitialized variable use

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Message-Id: <20250620112633.3505634-1-arnd@kernel.org>
Date: Fri, 20 Jun 2025 13:26:28 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] myri10ge: avoid uninitialized variable use

From: Arnd Bergmann <arnd@...db.de>

While compile testing on less common architectures, I noticed that gcc-10 on
s390 finds a bug that all other configurations seem to miss:

drivers/net/ethernet/myricom/myri10ge/myri10ge.c: In function 'myri10ge_set_multicast_list':
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:391:25: error: 'cmd.data0' is used uninitialized in this function [-Werror=uninitialized]
  391 |  buf->data0 = htonl(data->data0);
      |                         ^~
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:392:25: error: '*((void *)&cmd+4)' is used uninitialized in this function [-Werror=uninitialized]
  392 |  buf->data1 = htonl(data->data1);
      |                         ^~
drivers/net/ethernet/myricom/myri10ge/myri10ge.c: In function 'myri10ge_allocate_rings':
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:392:13: error: 'cmd.data1' is used uninitialized in this function [-Werror=uninitialized]
  392 |  buf->data1 = htonl(data->data1);
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:1939:22: note: 'cmd.data1' was declared here
 1939 |  struct myri10ge_cmd cmd;
      |                      ^~~
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:393:13: error: 'cmd.data2' is used uninitialized in this function [-Werror=uninitialized]
  393 |  buf->data2 = htonl(data->data2);
drivers/net/ethernet/myricom/myri10ge/myri10ge.c:1939:22: note: 'cmd.data2' was declared here
 1939 |  struct myri10ge_cmd cmd;

It would be nice to understand how to make other compilers catch this as
well, but for the moment I'll just shut up the warning by fixing the
undefined behavior in this driver.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/ethernet/myricom/myri10ge/myri10ge.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
index e611ff7fa3fa..f9d6ba381361 100644
--- a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
+++ b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
@@ -688,6 +688,9 @@ static int myri10ge_get_firmware_capabilities(struct myri10ge_priv *mgp)
 
 	/* probe for IPv6 TSO support */
 	mgp->features = NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_TSO;
+	cmd.data0 = 0,
+	cmd.data1 = 0,
+	cmd.data2 = 0,
 	status = myri10ge_send_cmd(mgp, MXGEFW_CMD_GET_MAX_TSO6_HDR_SIZE,
 				   &cmd, 0);
 	if (status == 0) {
@@ -834,6 +837,9 @@ myri10ge_change_promisc(struct myri10ge_priv *mgp, int promisc, int atomic)
 	int status, ctl;
 
 	ctl = promisc ? MXGEFW_ENABLE_PROMISC : MXGEFW_DISABLE_PROMISC;
+	cmd.data0 = 0;
+	cmd.data1 = 0;
+	cmd.data2 = 0;
 	status = myri10ge_send_cmd(mgp, ctl, &cmd, atomic);
 	if (status)
 		netdev_err(mgp->dev, "Failed to set promisc mode\n");
@@ -1946,6 +1952,8 @@ static int myri10ge_allocate_rings(struct myri10ge_slice_state *ss)
 	/* get ring sizes */
 	slice = ss - mgp->ss;
 	cmd.data0 = slice;
+	cmd.data1 = 0;
+	cmd.data2 = 0;
 	status = myri10ge_send_cmd(mgp, MXGEFW_CMD_GET_SEND_RING_SIZE, &cmd, 0);
 	tx_ring_size = cmd.data0;
 	cmd.data0 = slice;
@@ -2238,6 +2246,8 @@ static int myri10ge_get_txrx(struct myri10ge_priv *mgp, int slice)
 	status = 0;
 	if (slice == 0 || (mgp->dev->real_num_tx_queues > 1)) {
 		cmd.data0 = slice;
+		cmd.data1 = 0;
+		cmd.data2 = 0;
 		status = myri10ge_send_cmd(mgp, MXGEFW_CMD_GET_SEND_OFFSET,
 					   &cmd, 0);
 		ss->tx.lanai = (struct mcp_kreq_ether_send __iomem *)
@@ -2312,6 +2322,7 @@ static int myri10ge_open(struct net_device *dev)
 	if (mgp->num_slices > 1) {
 		cmd.data0 = mgp->num_slices;
 		cmd.data1 = MXGEFW_SLICE_INTR_MODE_ONE_PER_SLICE;
+		cmd.data2 = 0;
 		if (mgp->dev->real_num_tx_queues > 1)
 			cmd.data1 |= MXGEFW_SLICE_ENABLE_MULTIPLE_TX_QUEUES;
 		status = myri10ge_send_cmd(mgp, MXGEFW_CMD_ENABLE_RSS_QUEUES,
@@ -2414,6 +2425,8 @@ static int myri10ge_open(struct net_device *dev)
 
 	/* now give firmware buffers sizes, and MTU */
 	cmd.data0 = dev->mtu + ETH_HLEN + VLAN_HLEN;
+	cmd.data1 = 0;
+	cmd.data2 = 0;
 	status = myri10ge_send_cmd(mgp, MXGEFW_CMD_SET_MTU, &cmd, 0);
 	cmd.data0 = mgp->small_bytes;
 	status |=
@@ -2956,6 +2969,9 @@ static void myri10ge_set_multicast_list(struct net_device *dev)
 
 	/* Disable multicast filtering */
 
+	cmd.data0 = 0;
+	cmd.data1 = 0;
+	cmd.data2 = 0;
 	err = myri10ge_send_cmd(mgp, MXGEFW_ENABLE_ALLMULTI, &cmd, 1);
 	if (err != 0) {
 		netdev_err(dev, "Failed MXGEFW_ENABLE_ALLMULTI, error status: %d\n",
-- 
2.39.5