linux-cve-announce - CVE-2025-68329: tracing: Fix WARN_ON in tracing_buffers_mmap

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Message-ID: <2025122218-CVE-2025-68329-addf@gregkh>
Date: Mon, 22 Dec 2025 17:14:21 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68329: tracing: Fix WARN_ON in tracing_buffers_mmap_close for split VMAs

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

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

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

tracing: Fix WARN_ON in tracing_buffers_mmap_close for split VMAs

When a VMA is split (e.g., by partial munmap or MAP_FIXED), the kernel
calls vm_ops->close on each portion. For trace buffer mappings, this
results in ring_buffer_unmap() being called multiple times while
ring_buffer_map() was only called once.

This causes ring_buffer_unmap() to return -ENODEV on subsequent calls
because user_mapped is already 0, triggering a WARN_ON.

Trace buffer mappings cannot support partial mappings because the ring
buffer structure requires the complete buffer including the meta page.

Fix this by adding a may_split callback that returns -EINVAL to prevent
VMA splits entirely.

The Linux kernel CVE team has assigned CVE-2025-68329 to this issue.


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

	Issue introduced in 6.10 with commit cf9f0f7c4c5bb45e7bb270e48bab6f7837825a64 and fixed in 6.12.61 with commit 922fdd0b755a84f9933b3ca195f60092b6bb88ee
	Issue introduced in 6.10 with commit cf9f0f7c4c5bb45e7bb270e48bab6f7837825a64 and fixed in 6.17.11 with commit 45053c12c45f0fb8ef6ab95118dd928d2fec0255
	Issue introduced in 6.10 with commit cf9f0f7c4c5bb45e7bb270e48bab6f7837825a64 and fixed in 6.18 with commit b042fdf18e89a347177a49e795d8e5184778b5b6

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-2025-68329
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/trace.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/922fdd0b755a84f9933b3ca195f60092b6bb88ee
	https://git.kernel.org/stable/c/45053c12c45f0fb8ef6ab95118dd928d2fec0255
	https://git.kernel.org/stable/c/b042fdf18e89a347177a49e795d8e5184778b5b6