CVE-2026-97617: ring-buffer: Check resize_disabled before publishing the new subbuf order

CVE-2026-97617: ring-buffer: Check resize_disabled before publishing the new subbuf order

[Greg Kroah-Hartman]

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

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

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

ring-buffer: Check resize_disabled before publishing the new subbuf order

ring_buffer_subbuf_order_set() stores the new order and only then walks
the CPUs, returning -EBUSY if any of them has resizing disabled. A user
mapped buffer has resizing disabled, and __rb_map_vma() reads
buffer->subbuf_order without buffer->mutex, so an mmap of an already
mapped CPU racing the failing order change sizes the mapping with the
new order and inserts pages past the sub-buffer into the VMA.

Check the CPUs before storing the new order.

The Linux kernel CVE team has assigned CVE-2026-97617 to this issue.


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

	Issue introduced in 6.10 with commit 117c39200d9d760cbd5944bb89efb7b9c51965aa and fixed in 6.12.111 with commit f2099644e1b2a2c0805c5240d63ab0522d9d0174
	Issue introduced in 6.10 with commit 117c39200d9d760cbd5944bb89efb7b9c51965aa and fixed in 6.18.53 with commit 9fd4ea952e6ac12a63c3fe89f08ad02771aa2c06
	Issue introduced in 6.10 with commit 117c39200d9d760cbd5944bb89efb7b9c51965aa and fixed in 7.2.7 with commit 32bf47db9237c5b8b6f6aaa5356bb4c79d241f76
	Issue introduced in 6.10 with commit 117c39200d9d760cbd5944bb89efb7b9c51965aa and fixed in 7.3-rc3 with commit d860c67c051685abb0460b593b193f0f45f4fa92

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-2026-97617
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/f2099644e1b2a2c0805c5240d63ab0522d9d0174
	https://git.kernel.org/stable/c/9fd4ea952e6ac12a63c3fe89f08ad02771aa2c06
	https://git.kernel.org/stable/c/32bf47db9237c5b8b6f6aaa5356bb4c79d241f76
	https://git.kernel.org/stable/c/d860c67c051685abb0460b593b193f0f45f4fa92