CVE-2026-99187: perf: Fix perf_pmu_migrate_context() leaving events behind

CVE-2026-99187: perf: Fix perf_pmu_migrate_context() leaving events behind

[Greg Kroah-Hartman]

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

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

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

perf: Fix perf_pmu_migrate_context() leaving events behind

__perf_pmu_remove() walks the group leaders of a CPU and PMU with
perf_event_groups_for_cpu_pmu(), removing each one as it goes.
perf_remove_from_context() takes the leader out of the groups rbtree,
after which rb_next() on that node returns NULL, prematurely ending the
walk. Other groups stay behind in the source context.

On CPU hotplug, they are then torn down with the dying CPU. They keep
running until teardown, while the PMU's interrupt and migrated events
are on a new CPU, which drivers rely on never happening.

Walk ctx->event_list instead and pick out the PMU's events by their
pmu_ctx.

The Linux kernel CVE team has assigned CVE-2026-99187 to this issue.


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

	Issue introduced in 6.2 with commit bd27568117664b8b3e259721393df420ed51f57b and fixed in 6.18.59 with commit 3eb08f09bfb364051f51316da873c3bd51a839ef
	Issue introduced in 6.2 with commit bd27568117664b8b3e259721393df420ed51f57b and fixed in 7.2.13 with commit f5f0028764de322a3d04eda0d3b6389ca9847446
	Issue introduced in 6.2 with commit bd27568117664b8b3e259721393df420ed51f57b and fixed in 7.3 with commit e76b36b4be7160eaa14b416681e548b125702395

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-2026-99187
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:
	kernel/events/core.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/3eb08f09bfb364051f51316da873c3bd51a839ef
	https://git.kernel.org/stable/c/f5f0028764de322a3d04eda0d3b6389ca9847446
	https://git.kernel.org/stable/c/e76b36b4be7160eaa14b416681e548b125702395