CVE-2026-74593
Received Received - Intake

Deadlock in Linux Kernel Sched Ext

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Take cgroup_lock() first in scx_cgroup_lock() scx_cgroup_lock() write-locks scx_cgroup_ops_rwsem and then takes cgroup_lock(), which can deadlock through kernfs: scx enable/disable cgroup rmdir cpu.weight write ------------------ ------------ ---------------- cgroup_lock() percpu_down_write(rwsem) cgroup_lock() kernfs_get_active() percpu_down_read(rwsem) kernfs_drain() The enable path waits for the rmdir to release cgroup_mutex. The rmdir, deactivating the cpu controller's files, waits in kernfs_drain() for the write's active reference. The write, in scx_group_set_weight(), waits for the rwsem behind the pending writer. Take cgroup_lock() first. The set_* paths take no cgroup locks inside the read side, so a pending write-lock then only waits for read sections that always run to completion, and no dependency from the rwsem back to cgroup_mutex remains.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74593
EUVD
EUVD-2026-64530

Affected Vendors & Products

Currently, no data is known.

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability where a deadlock can occur in the sched_ext subsystem. The issue arises when scx_cgroup_lock() attempts to lock cgroup_lock() after already holding scx_cgroup_ops_rwsem, creating a circular dependency with kernfs operations. This can lead to system hangs during operations like enabling/disabling sched_ext, removing cgroups, or writing to cpu.weight.

Detection Guidance

This vulnerability is specific to the Linux kernel's sched_ext subsystem and requires kernel-level inspection. Detection involves checking kernel logs for deadlocks or hangs related to cgroup operations or sched_ext. Commands like dmesg | grep -i 'scx\|cgroup\|deadlock' or journalctl -k | grep -i 'scx\|cgroup\|deadlock' may help identify issues.

Impact Analysis

The deadlock could cause system freezes or crashes when performing operations that interact with cgroups and sched_ext. This might lead to unresponsive systems, failed process scheduling, or kernel panics during routine tasks like process management or resource allocation.

Mitigation Strategies

Apply the latest Linux kernel update that resolves this issue. If immediate patching is not possible, disable the sched_ext subsystem by setting CONFIG_SCHED_CLASS_EXT to 'n' in the kernel configuration and recompiling. Monitor kernel logs for signs of deadlocks or hangs.

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