CVE-2023-53798: In the Linux kernel, the following vulnerability has been resolved:  ethtool: Fix uninitialized number of lanes  It is not possible to set the number of lanes when setting link modes using the legacy IOCTL ethtool interface. Since 'struct ethtool_link_ksettings' is not initialized in this path, drivers receive an uninitialized number of lanes in 'struct ethtool_link_ksettings::lanes'.  When this information is later queried from drivers, it results in the ethtool code making decisions based on uninitialized memory, leading to the following KMSAN splat [1]. In practice, this most likely only happens with the tun driver that simply returns whatever it got in the set operation.  As far as I can tell, this uninitialized memory is not leaked to user space thanks to the 'ethtool_ops->cap_link_lanes_supported' check in linkmodes_prepare_data().  Fix by initializing the structure in the IOCTL path. Did not find any more call sites that pass an uninitialized structure when calling 'ethtool_ops::set_link_ksettings()'.  [1] BUG: KMSAN: uninit-value in ethnl_update_linkmodes net/ethtool/linkmodes.c:273 [inline] BUG: KMSAN: uninit-value in ethnl_set_linkmodes+0x190b/0x19d0 net/ethtool/linkmodes.c:333  ethnl_update_linkmodes net/ethtool/linkmodes.c:273 [inline]  ethnl_set_linkmodes+0x190b/0x19d0 net/ethtool/linkmodes.c:333  ethnl_default_set_doit+0x88d/0xde0 net/ethtool/netlink.c:640  genl_family_rcv_msg_doit net/netlink/genetlink.c:968 [inline]  genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]  genl_rcv_msg+0x141a/0x14c0 net/netlink/genetlink.c:1065  netlink_rcv_skb+0x3f8/0x750 net/netlink/af_netlink.c:2577  genl_rcv+0x40/0x60 net/netlink/genetlink.c:1076  netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]  netlink_unicast+0xf41/0x1270 net/netlink/af_netlink.c:1365  netlink_sendmsg+0x127d/0x1430 net/netlink/af_netlink.c:1942  sock_sendmsg_nosec net/socket.c:724 [inline]  sock_sendmsg net/socket.c:747 [inline]  ____sys_sendmsg+0xa24/0xe40 net/socket.c:2501  ___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2555  __sys_sendmsg net/socket.c:2584 [inline]  __do_sys_sendmsg net/socket.c:2593 [inline]  __se_sys_sendmsg net/socket.c:2591 [inline]  __x64_sys_sendmsg+0x36b/0x540 net/socket.c:2591  do_syscall_x64 arch/x86/entry/common.c:50 [inline]  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80  entry_SYSCALL_64_after_hwframe+0x63/0xcd  Uninit was stored to memory at:  tun_get_link_ksettings+0x37/0x60 drivers/net/tun.c:3544  __ethtool_get_link_ksettings+0x17b/0x260 net/ethtool/ioctl.c:441  ethnl_set_linkmodes+0xee/0x19d0 net/ethtool/linkmodes.c:327  ethnl_default_set_doit+0x88d/0xde0 net/ethtool/netlink.c:640  genl_family_rcv_msg_doit net/netlink/genetlink.c:968 [inline]  genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]  genl_rcv_msg+0x141a/0x14c0 net/netlink/genetlink.c:1065  netlink_rcv_skb+0x3f8/0x750 net/netlink/af_netlink.c:2577  genl_rcv+0x40/0x60 net/netlink/genetlink.c:1076  netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]  netlink_unicast+0xf41/0x1270 net/netlink/af_netlink.c:1365  netlink_sendmsg+0x127d/0x1430 net/netlink/af_netlink.c:1942  sock_sendmsg_nosec net/socket.c:724 [inline]  sock_sendmsg net/socket.c:747 [inline]  ____sys_sendmsg+0xa24/0xe40 net/socket.c:2501  ___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2555  __sys_sendmsg net/socket.c:2584 [inline]  __do_sys_sendmsg net/socket.c:2593 [inline]  __se_sys_sendmsg net/socket.c:2591 [inline]  __x64_sys_sendmsg+0x36b/0x540 net/socket.c:2591  do_syscall_x64 arch/x86/entry/common.c:50 [inline]  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80  entry_SYSCALL_64_after_hwframe+0x63/0xcd  Uninit was stored to memory at:  tun_set_link_ksettings+0x37/0x60 drivers/net/tun.c:3553  ethtool_set_link_ksettings+0x600/0x690 net/ethtool/ioctl.c:609  __dev_ethtool net/ethtool/ioctl.c:3024 [inline]  dev_ethtool+0x1db9/0x2a70 net/ethtool/ioctl.c:3078  dev_ioctl+0xb07/0x1270 net/core/dev_ioctl.c:524  sock_do_ioctl+0x295/0x540 net/socket.c:1213  sock_i ---truncated---