CVE-2026-74749
Received Received - Intake

Kernel Hard Lockup in Linux rseq Due to Interrupt Handling

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: rseq: Prevent hard lockup on granted time slice extension __exit_to_user_mode_loop() invokes rseq_grant_timeslice_extension() with interrupts enabled. If the extension is granted it invokes hrtimer_rearm_deferred_tif() to ensure that a pending deferred hrtimer rearm is handled before exiting to user space. Though this invokes __hrtimer_rearm_deferred() which expects to be invoked with interrupts disabled as it takes hrtimer_cpu_base::lock with raw_spin_lock(). That's a livelock waiting to happen and caught by lockdep: WARNING: ./include/linux/hrtimer_rearm.h:17 at irqentry_exit, CPU#1: slice_test WARNING: inconsistent lock state inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage. Prevent this by disabling interrupts around the invocation of hrtimer_rearm_deferred_tif() in rseq_grant_timeslice_extension(). [ tglx: Massaged change log ]

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Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-74749
EUVD
EUVD-2026-66579

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a hard lockup risk during time slice extension in the rseq subsystem. When exiting to user mode, interrupts are enabled while calling rseq_grant_timeslice_extension(), which may trigger a livelock due to improper interrupt handling in hrtimer_rearm_deferred_tif().

Detection Guidance

This vulnerability is specific to the Linux kernel and may not have direct detection commands. However, monitoring for kernel lockups or warnings related to hrtimer_cpu_base::lock or rseq_grant_timeslice_extension() in system logs could indicate exploitation. Check dmesg or journalctl for lockdep warnings or hard lockup messages.

Impact Analysis

The vulnerability can cause system freezes or unresponsiveness (hard lockups) on affected Linux systems. This may lead to crashes, degraded performance, or denial of service if the livelock condition is triggered during normal operations.

Mitigation Strategies

Update the Linux kernel to the latest stable version that includes the fix for this vulnerability. This resolves the issue by ensuring interrupts are disabled during hrtimer_rearm_deferred_tif() invocation in rseq_grant_timeslice_extension().

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