linux-cve-announce - CVE-2025-38177: sch_hfsc: make hfsc_qlen

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Message-ID: <2025070411-CVE-2025-38177-bd6c@gregkh>
Date: Fri,  4 Jul 2025 14:47:12 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38177: sch_hfsc: make hfsc_qlen_notify() idempotent

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

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

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

sch_hfsc: make hfsc_qlen_notify() idempotent

hfsc_qlen_notify() is not idempotent either and not friendly
to its callers, like fq_codel_dequeue(). Let's make it idempotent
to ease qdisc_tree_reduce_backlog() callers' life:

1. update_vf() decreases cl->cl_nactive, so we can check whether it is
non-zero before calling it.

2. eltree_remove() always removes RB node cl->el_node, but we can use
   RB_EMPTY_NODE() + RB_CLEAR_NODE() to make it safe.

The Linux kernel CVE team has assigned CVE-2025-38177 to this issue.


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

	Fixed in 6.1.138 with commit 0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87
	Fixed in 6.6.90 with commit 9030a91235ae4845ec71902c3e0cecfc9ed1f2df
	Fixed in 6.12.28 with commit d06476714d2819b550e0cc39222347e2c8941c9d
	Fixed in 6.14.6 with commit c1175c4ad01dbc9c979d099861fa90a754f72059
	Fixed in 6.15 with commit 51eb3b65544c9efd6a1026889ee5fb5aa62da3bb

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-2025-38177
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:
	net/sched/sch_hfsc.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/0475c85426b18eccdcb7f9fb58d8f8e9c6c58c87
	https://git.kernel.org/stable/c/9030a91235ae4845ec71902c3e0cecfc9ed1f2df
	https://git.kernel.org/stable/c/d06476714d2819b550e0cc39222347e2c8941c9d
	https://git.kernel.org/stable/c/c1175c4ad01dbc9c979d099861fa90a754f72059
	https://git.kernel.org/stable/c/51eb3b65544c9efd6a1026889ee5fb5aa62da3bb