linux-cve-announce - CVE-2025-38564: perf/core: Handle buffer mapping fail correctly in perf

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Message-ID: <2025081908-CVE-2025-38564-efa3@gregkh>
Date: Tue, 19 Aug 2025 19:18:11 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38564: perf/core: Handle buffer mapping fail correctly in perf_mmap()

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

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

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

perf/core: Handle buffer mapping fail correctly in perf_mmap()

After successful allocation of a buffer or a successful attachment to an
existing buffer perf_mmap() tries to map the buffer read only into the page
table. If that fails, the already set up page table entries are zapped, but
the other perf specific side effects of that failure are not handled.  The
calling code just cleans up the VMA and does not invoke perf_mmap_close().

This leaks reference counts, corrupts user->vm accounting and also results
in an unbalanced invocation of event::event_mapped().

Cure this by moving the event::event_mapped() invocation before the
map_range() call so that on map_range() failure perf_mmap_close() can be
invoked without causing an unbalanced event::event_unmapped() call.

perf_mmap_close() undoes the reference counts and eventually frees buffers.

The Linux kernel CVE team has assigned CVE-2025-38564 to this issue.

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

	Issue introduced in 6.14 with commit b709eb872e19a19607bbb6d2975bc264d59735cf and fixed in 6.15.10 with commit 831e1c90a5d72e6977a57c44f47c46b73a438695
	Issue introduced in 6.14 with commit b709eb872e19a19607bbb6d2975bc264d59735cf and fixed in 6.16.1 with commit a9025f73c88d9d6e125743a43afc569da3ce5328
	Issue introduced in 6.14 with commit b709eb872e19a19607bbb6d2975bc264d59735cf and fixed in 6.17-rc1 with commit f74b9f4ba63ffdf597aaaa6cad7e284cb8e04820

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-2025-38564
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/831e1c90a5d72e6977a57c44f47c46b73a438695
	https://git.kernel.org/stable/c/a9025f73c88d9d6e125743a43afc569da3ce5328
	https://git.kernel.org/stable/c/f74b9f4ba63ffdf597aaaa6cad7e284cb8e04820