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Message-ID: <2025120942-CVE-2023-53798-7845@gregkh>
Date: Tue,  9 Dec 2025 09:02:19 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53798: ethtool: Fix uninitialized number of lanes

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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_ioctl+0x729/0xd90 net/socket.c:1316
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0x222/0x400 fs/ioctl.c:856
 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:856
 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

Local variable link_ksettings created at:
 ethtool_set_link_ksettings+0x54/0x690 net/ethtool/ioctl.c:577
 __dev_ethtool net/ethtool/ioctl.c:3024 [inline]
 dev_ethtool+0x1db9/0x2a70 net/ethtool/ioctl.c:3078

The Linux kernel CVE team has assigned CVE-2023-53798 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.12 with commit 012ce4dd3102a0f4d80167de343e9d44b257c1b8 and fixed in 5.15.112 with commit da81af0ef8092ecacd87fac3229c29e2e0ce39fd
	Issue introduced in 5.12 with commit 012ce4dd3102a0f4d80167de343e9d44b257c1b8 and fixed in 6.1.29 with commit 942a2a0184f7bb1c1ae4bbc556559c86c054b0d2
	Issue introduced in 5.12 with commit 012ce4dd3102a0f4d80167de343e9d44b257c1b8 and fixed in 6.2.16 with commit 6456d80045d6de47734b1a3879c91f72af186529
	Issue introduced in 5.12 with commit 012ce4dd3102a0f4d80167de343e9d44b257c1b8 and fixed in 6.3.3 with commit 72808c4ab5fd01bf1214195005e15b434bf55cef
	Issue introduced in 5.12 with commit 012ce4dd3102a0f4d80167de343e9d44b257c1b8 and fixed in 6.4 with commit 9ad685dbfe7e856bbf17a7177b64676d324d6ed7

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2023-53798
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/ethtool/ioctl.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/da81af0ef8092ecacd87fac3229c29e2e0ce39fd
	https://git.kernel.org/stable/c/942a2a0184f7bb1c1ae4bbc556559c86c054b0d2
	https://git.kernel.org/stable/c/6456d80045d6de47734b1a3879c91f72af186529
	https://git.kernel.org/stable/c/72808c4ab5fd01bf1214195005e15b434bf55cef
	https://git.kernel.org/stable/c/9ad685dbfe7e856bbf17a7177b64676d324d6ed7

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