CVE-2026-68286: drop_monitor: perform u64_stats updates under IRQ-disabled section

From: Greg Kroah-Hartman <[email protected]>

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

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

drop_monitor: perform u64_stats updates under IRQ-disabled section

In net_dm_packet_trace_kfree_skb_hit() and net_dm_hw_trap_packet_probe(),
u64_stats_update_begin() / u64_stats_inc() / u64_stats_update_end() were
called after spin_unlock_irqrestore(&...drop_queue.lock, flags), when local
IRQs had already been re-enabled.

Tracepoint probes can execute in IRQ or softirq context. On 32-bit
architectures, u64_stats_update_begin() disables preemption but not interrupts,
relying on seqcount writes. If a nested interrupt occurs on the same CPU during
the 64-bit stats update, the reentrant seqcount update can corrupt the
seqcount state or stats value.

Fix this by performing the 64-bit per-CPU stats update before releasing
drop_queue.lock via spin_unlock_irqrestore(), ensuring local interrupts remain
disabled during the u64_stats update.

The Linux kernel CVE team has assigned CVE-2026-68286 to this issue.


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

	Issue introduced in 5.4 with commit e9feb58020f952f7d9de785ede9a7d54ab1eda5c and fixed in 7.1.6 with commit d5e2cd2bc8ae36617346b3a54ee9da61d866bf92
	Issue introduced in 5.4 with commit e9feb58020f952f7d9de785ede9a7d54ab1eda5c and fixed in 7.2-rc5 with commit fd098a23bf8fda7eae48db9b06e7c34fc4d228fa

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-2026-68286
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/d5e2cd2bc8ae36617346b3a54ee9da61d866bf92
	https://git.kernel.org/stable/c/fd098a23bf8fda7eae48db9b06e7c34fc4d228fa