CVE-2026-68287: drop_monitor: fix size calculations for 64-bit attributes

CVE-2026-68287: drop_monitor: fix size calculations for 64-bit attributes

[Greg Kroah-Hartman]

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

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

In the Linux kernel, the following vulnerability has been resolved:

drop_monitor: fix size calculations for 64-bit attributes

net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() use
nla_put_u64_64bit() to append 64-bit attributes (NET_DM_ATTR_PC and
NET_DM_ATTR_TIMESTAMP).

On 32-bit architectures without CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
nla_put_u64_64bit() may append a 4-byte NET_DM_ATTR_PAD attribute for
64-bit alignment.

However, net_dm_packet_report_size() and net_dm_hw_packet_report_size()
used nla_total_size(sizeof(u64)) instead of nla_total_size_64bit(sizeof(u64)),
budgeting 12 bytes instead of up to 16 bytes.

This under-estimation of SKB size can lead to an skb_over_panic() when
__nla_reserve() or skb_put() is subsequently called.

Fix this by using nla_total_size_64bit(sizeof(u64)) in both size calculations.

The Linux kernel CVE team has assigned CVE-2026-68287 to this issue.


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

	Issue introduced in 5.4 with commit ca30707dee2bc8bc81cfd8b4277fe90f7ca6df1f and fixed in 7.1.6 with commit 4a9e30764e80693bcf875c776170edce20f94fe0
	Issue introduced in 5.4 with commit ca30707dee2bc8bc81cfd8b4277fe90f7ca6df1f and fixed in 7.2-rc5 with commit 7089f7ab99c89f443c92d8fcc585e63f2727f0b3

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-2026-68287
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/core/drop_monitor.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/4a9e30764e80693bcf875c776170edce20f94fe0
	https://git.kernel.org/stable/c/7089f7ab99c89f443c92d8fcc585e63f2727f0b3