linux-cve-announce - CVE-2024-50207: ring-buffer: Fix reader locking when changing the sub buffer order

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Message-ID: <2024110806-CVE-2024-50207-6f39@gregkh>
Date: Fri,  8 Nov 2024 07:08:08 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50207: ring-buffer: Fix reader locking when changing the sub buffer order

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

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

ring-buffer: Fix reader locking when changing the sub buffer order

The function ring_buffer_subbuf_order_set() updates each
ring_buffer_per_cpu and installs new sub buffers that match the requested
page order. This operation may be invoked concurrently with readers that
rely on some of the modified data, such as the head bit (RB_PAGE_HEAD), or
the ring_buffer_per_cpu.pages and reader_page pointers. However, no
exclusive access is acquired by ring_buffer_subbuf_order_set(). Modifying
the mentioned data while a reader also operates on them can then result in
incorrect memory access and various crashes.

Fix the problem by taking the reader_lock when updating a specific
ring_buffer_per_cpu in ring_buffer_subbuf_order_set().

The Linux kernel CVE team has assigned CVE-2024-50207 to this issue.

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

	Issue introduced in 6.8 with commit 8e7b58c27b3c and fixed in 6.11.6 with commit a569290525a0
	Issue introduced in 6.8 with commit 8e7b58c27b3c and fixed in 6.12-rc4 with commit 09661f75e75c

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-2024-50207
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/a569290525a05162d5dd26d9845591eaf46e5802
	https://git.kernel.org/stable/c/09661f75e75cb6c1d2d8326a70c311d46729235f