From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-43438: sched_ext: Remove redundant css_put() in scx_cgroup_init()
Date: Fri, 8 May 2026 16:22:47 +0200 [thread overview]
Message-ID: <2026050853-CVE-2026-43438-f2f2@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Remove redundant css_put() in scx_cgroup_init()
The iterator css_for_each_descendant_pre() walks the cgroup hierarchy
under cgroup_lock(). It does not increment the reference counts on
yielded css structs.
According to the cgroup documentation, css_put() should only be used
to release a reference obtained via css_get() or css_tryget_online().
Since the iterator does not use either of these to acquire a reference,
calling css_put() in the error path of scx_cgroup_init() causes a
refcount underflow.
Remove the unbalanced css_put() to prevent a potential Use-After-Free
(UAF) vulnerability.
The Linux kernel CVE team has assigned CVE-2026-43438 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 6.12.78 with commit cc095cd305fddbe25a968e4a78436ff9476cf0f6
Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 6.18.19 with commit 6eaaa67d6998f6c30c462b140db8c062e07ec473
Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 6.19.9 with commit bf50f3285eda8a0173625fcdb5f183f96e1008cd
Issue introduced in 6.12 with commit 8195136669661fdfe54e9a8923c33b31c92fc1da and fixed in 7.0 with commit 1336b579f6079fb8520be03624fcd9ba443c930b
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-2026-43438
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/cc095cd305fddbe25a968e4a78436ff9476cf0f6
https://git.kernel.org/stable/c/6eaaa67d6998f6c30c462b140db8c062e07ec473
https://git.kernel.org/stable/c/bf50f3285eda8a0173625fcdb5f183f96e1008cd
https://git.kernel.org/stable/c/1336b579f6079fb8520be03624fcd9ba443c930b
reply other threads:[~2026-05-08 14:25 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2026050853-CVE-2026-43438-f2f2@gregkh \
--to=gregkh@linuxfoundation.org \
--cc=cve@kernel.org \
--cc=gregkh@kernel.org \
--cc=linux-cve-announce@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox