CVE-2024-43870: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: perf: Fix event leak upon exit When a task is scheduled out, pending sigtrap deliveries are deferred to the target task upon resume to userspace via task_work. However failures while adding an event's callback to the task_work engine are ignored. And since the last call for events exit happen after task work is eventually closed, there is a small window during which pending sigtrap can be queued though ignored, leaking the event refcount addition such as in the following scenario: TASK A ----- do_exit() exit_task_work(tsk); <IRQ> perf_event_overflow() event->pending_sigtrap = pending_id; irq_work_queue(&event->pending_irq); </IRQ> =========> PREEMPTION: TASK A -> TASK B event_sched_out() event->pending_sigtrap = 0; atomic_long_inc_not_zero(&event->refcount) // FAILS: task work has exited task_work_add(&event->pending_task) [...] <IRQ WORK> perf_pending_irq() // early return: event->oncpu = -1 </IRQ WORK> [...] =========> TASK B -> TASK A perf_event_exit_task(tsk) perf_event_exit_event() free_event() WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1) // leak event due to unexpected refcount == 2 As a result the event is never released while the task exits. Fix this with appropriate task_work_add()'s error handling.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-401 CWE-401

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.15.84 — 5.15.165
linux	linux_kernel	6.0.14 — 6.1
linux	linux_kernel	6.1.1 — 6.1.103
linux	linux_kernel	6.2 — 6.6.44
linux	linux_kernel	6.7 — 6.10.3
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/05d3fd599594abf79aad4484bccb2b26e1cb0b51 https://git.kernel.org/stable/c/2fd5ad3f310de22836cdacae919dd99d758a1f1b https://git.kernel.org/stable/c/3d7a63352a93bdb8a1cdf29606bf617d3ac1c22a https://git.kernel.org/stable/c/67fad724f1b568b356c1065d50df46e6b30eb2f7 https://git.kernel.org/stable/c/70882d7fa74f0731492a0d493e8515a4f7131831

Other References

https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html

Frequently Asked Questions

What is CVE-2024-43870? +

In the Linux kernel, the following vulnerability has been resolved: perf: Fix event leak upon exit When a task is scheduled out, pending sigtrap deliveries are deferred to the target task upon resume to userspace via task_work. However failures while adding an event's callback to the task_work engine are ignored. And since the last call for events exit happen after task work is eventually closed, there is a small window during which pending sigtrap can be queued though ignored, leaking the event refcount addition such as in the following scenario: TASK A ----- do_exit() exit_task_work(tsk); <IRQ> perf_event_overflow() event->pending_sigtrap = pending_id; irq_work_queue(&event->pending_irq); </IRQ> =========> PREEMPTION: TASK A -> TASK B event_sched_out() event->pending_sigtrap = 0; atomic_long_inc_not_zero(&event->refcount) // FAILS: task work has exited task_work_add(&event->pending_task) [...] <IRQ WORK> perf_pending_irq() // early return: event->oncpu = -1 </IRQ WORK> [...] =========> TASK B -> TASK A perf_event_exit_task(tsk) perf_event_exit_event() free_event() WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1) // leak event due to unexpected refcount == 2 As a result the event is never released while the task exits. Fix this with appropriate task_work_add()'s error handling. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2024-43870? +

CVE-2024-43870 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2024-43870? +

CVE-2024-43870 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-43870? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2024-43870