From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-93220: sched_ext: Keep kick_sync waiting on the rq's own CPU
Date: Thu, 24 Sep 2026 17:10:56 +0200 [thread overview]
Message-ID: <2026092446-CVE-2026-93220-bcdf@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Keep kick_sync waiting on the rq's own CPU
kick_sync_wait_bal_cb() assumes it runs on the rq's CPU from the
__schedule() tail: the snapshots it compares against live in that CPU's
percpu area and the busy-wait runs with the rq lock dropped and IRQs
enabled.
However, dispatch can now drop the rq lock while the callback sits queued,
and rq lock takers in that window (the sched class change paths, the scx
task iterator) flush pending balance callbacks on release, running the
callback on a foreign CPU. Such a run compares against unrelated snapshots
and can deadlock when the executing CPU is itself a wait target.
Bail on a foreign CPU and leave the wait state alone. The wait only observes
progress that the resched kicks already guarantee and the rq's next wait
picks up the stale cpus_to_sync bits.
The Linux kernel CVE team has assigned CVE-2026-93220 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.19 with commit 4c95380701f58b8112f0b891de8d160e4199e19d and fixed in 7.2.4 with commit c736ea0fe7b4df920da6bd43a81c5eeecadcc8be
Issue introduced in 6.19 with commit 4c95380701f58b8112f0b891de8d160e4199e19d and fixed in 7.3-rc1 with commit e0253dd04beb03e79477c5ef4768b11135687206
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-2026-93220
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/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/c736ea0fe7b4df920da6bd43a81c5eeecadcc8be
https://git.kernel.org/stable/c/e0253dd04beb03e79477c5ef4768b11135687206
reply other threads:[~2026-09-24 15:12 UTC|newest]
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