RDMA/core: Fix uninit-value access in ib_get_eth_speed()

KMSAN reported the following uninit-value access issue:

lo speed is unknown, defaulting to 1000
=====================================================
BUG: KMSAN: uninit-value in ib_get_width_and_speed drivers/infiniband/core/verbs.c:1889 [inline]
BUG: KMSAN: uninit-value in ib_get_eth_speed+0x546/0xaf0 drivers/infiniband/core/verbs.c:1998
 ib_get_width_and_speed drivers/infiniband/core/verbs.c:1889 [inline]
 ib_get_eth_speed+0x546/0xaf0 drivers/infiniband/core/verbs.c:1998
 siw_query_port drivers/infiniband/sw/siw/siw_verbs.c:173 [inline]
 siw_get_port_immutable+0x6f/0x120 drivers/infiniband/sw/siw/siw_verbs.c:203
 setup_port_data drivers/infiniband/core/device.c:848 [inline]
 setup_device drivers/infiniband/core/device.c:1244 [inline]
 ib_register_device+0x1589/0x1df0 drivers/infiniband/core/device.c:1383
 siw_device_register drivers/infiniband/sw/siw/siw_main.c:72 [inline]
 siw_newlink+0x129e/0x13d0 drivers/infiniband/sw/siw/siw_main.c:490
 nldev_newlink+0x8fd/0xa60 drivers/infiniband/core/nldev.c:1763
 rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
 rdma_nl_rcv+0xe8a/0x1120 drivers/infiniband/core/netlink.c:259
 netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]
 netlink_unicast+0xf4b/0x1230 net/netlink/af_netlink.c:1368
 netlink_sendmsg+0x1242/0x1420 net/netlink/af_netlink.c:1910
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x997/0xd60 net/socket.c:2588
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2642
 __sys_sendmsg net/socket.c:2671 [inline]
 __do_sys_sendmsg net/socket.c:2680 [inline]
 __se_sys_sendmsg net/socket.c:2678 [inline]
 __x64_sys_sendmsg+0x2fa/0x4a0 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Local variable lksettings created at:
 ib_get_eth_speed+0x4b/0xaf0 drivers/infiniband/core/verbs.c:1974
 siw_query_port drivers/infiniband/sw/siw/siw_verbs.c:173 [inline]
 siw_get_port_immutable+0x6f/0x120 drivers/infiniband/sw/siw/siw_verbs.c:203

CPU: 0 PID: 11257 Comm: syz-executor.1 Not tainted 6.6.0-14500-g1c41041124bd Rust-for-Linux#10
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
=====================================================

If __ethtool_get_link_ksettings() fails, `netdev_speed` is set to the
default value, SPEED_1000. In this case, if `lanes` field of struct
ethtool_link_ksettings is not initialized, an uninitialized value is passed
to ib_get_width_and_speed(). This causes the above issue. This patch
resolves the issue by initializing `lanes` to 0.

Fixes: cb06b6b ("RDMA/core: Get IB width and speed from netdev")
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Link: https://lore.kernel.org/r/20231108143113.1360567-1-syoshida@redhat.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/core/verbs.c

@@ -1971,7 +1971,7 @@ int ib_get_eth_speed(struct ib_device *dev, u32 port_num, u16 *speed, u8 *width)
 	int rc;
 	u32 netdev_speed;
 	struct net_device *netdev;
-	struct ethtool_link_ksettings lksettings;
+	struct ethtool_link_ksettings lksettings = {};
 
 	if (rdma_port_get_link_layer(dev, port_num) != IB_LINK_LAYER_ETHERNET)
 		return -EINVAL;