linux-cve-announce - CVE-2025-21657: sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops

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Message-ID: <2025012131-CVE-2025-21657-5f7d@gregkh>
Date: Tue, 21 Jan 2025 13:18:36 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21657: sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass()

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

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

sched_ext: Replace rq_lock() to raw_spin_rq_lock() in scx_ops_bypass()

scx_ops_bypass() iterates all CPUs to re-enqueue all the scx tasks.
For each CPU, it acquires a lock using rq_lock() regardless of whether
a CPU is offline or the CPU is currently running a task in a higher
scheduler class (e.g., deadline). The rq_lock() is supposed to be used
for online CPUs, and the use of rq_lock() may trigger an unnecessary
warning in rq_pin_lock(). Therefore, replace rq_lock() to
raw_spin_rq_lock() in scx_ops_bypass().

Without this change, we observe the following warning:

===== START =====
[    6.615205] rq->balance_callback && rq->balance_callback != &balance_push_callback
[    6.615208] WARNING: CPU: 2 PID: 0 at kernel/sched/sched.h:1730 __schedule+0x1130/0x1c90
=====  END  =====

The Linux kernel CVE team has assigned CVE-2025-21657 to this issue.


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

	Issue introduced in 6.12 with commit 0e7ffff1b8117b05635c87d3c9099f6aa9c9b689 and fixed in 6.12.10 with commit d9e446dd63cee7161717a6a8414ba9c6435af764
	Issue introduced in 6.12 with commit 0e7ffff1b8117b05635c87d3c9099f6aa9c9b689 and fixed in 6.13 with commit 6268d5bc10354fc2ab8d44a0cd3b042d49a0417e

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-2025-21657
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/sched/ext.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/d9e446dd63cee7161717a6a8414ba9c6435af764
	https://git.kernel.org/stable/c/6268d5bc10354fc2ab8d44a0cd3b042d49a0417e