CVE-2026-89501: ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

CVE-2026-89501: ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

[Greg Kroah-Hartman]

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

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

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

ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

Because, ring_buffer_subbuf_order_set() can clear cpu_buffer->free_page,
hold cpu_buffer->lock to prevent races with
ring_buffer_alloc_read_page() and ring_buffer_free_read_page().

The Linux kernel CVE team has assigned CVE-2026-89501 to this issue.


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

	Issue introduced in 6.8 with commit 8e7b58c27b3c567316a51079b375b846f9223bba and fixed in 6.12.109 with commit 8a496aaa3da6e8d545896c2370c7e617cc931ae2
	Issue introduced in 6.8 with commit 8e7b58c27b3c567316a51079b375b846f9223bba and fixed in 6.18.50 with commit 6fcb0b745a0b80df62eae4a93ce52a2d061f4ac2
	Issue introduced in 6.8 with commit 8e7b58c27b3c567316a51079b375b846f9223bba and fixed in 7.2.4 with commit bf242baf58de03467f226c8e29554c9495dca7fc
	Issue introduced in 6.8 with commit 8e7b58c27b3c567316a51079b375b846f9223bba and fixed in 7.3-rc1 with commit 24974bd0da1b47fd56c975533ead50abf754e74d

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-2026-89501
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/trace/ring_buffer.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/8a496aaa3da6e8d545896c2370c7e617cc931ae2
	https://git.kernel.org/stable/c/6fcb0b745a0b80df62eae4a93ce52a2d061f4ac2
	https://git.kernel.org/stable/c/bf242baf58de03467f226c8e29554c9495dca7fc
	https://git.kernel.org/stable/c/24974bd0da1b47fd56c975533ead50abf754e74d