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Time-of-check Time-of-use (TOCTOU) Affecting kernel-tools-devel package, versions <1:6.1.188-233.385.amzn2023

Severity

 Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.13% (2nd percentile)

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  • Snyk IDSNYK-AMZN2023-KERNELTOOLSDEVEL-20872354
  • published13 Oct 2026
  • disclosed11 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 11 Sep 2026

CVE-2026-89508  (opens in a new tab)
CWE-367  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 kernel-tools-devel to version 1:6.1.188-233.385.amzn2023 or higher.
This issue was patched in ALAS2023-2026-3197.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-tools-devel package and not the kernel-tools-devel package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

RDMA/ucma: Lock the handler in ucma_set_ib_path()

ucma_set_ib_path() calls ucma_event_handler() straight from the write() path, without the handler lock that keeps ctx->file stable while a uevent is queued. The handler re-reads ctx->file for every dereference:

mutex_lock(&amp;ctx-&gt;file-&gt;mut);			/* file A */
list_add_tail(&amp;uevent-&gt;list, &amp;ctx-&gt;file-&gt;event_list);	/* file B */
mutex_unlock(&amp;ctx-&gt;file-&gt;mut);			/* file B */
wake_up_interruptible(&amp;ctx-&gt;file-&gt;poll_wait);	/* file B */

A concurrent ucma_migrate_id() reassigns ctx->file while the SET_OPTION caller sleeps in mutex_lock(), so the list_add_tail() lands on file B's event_list while only file A's mutex is held, racing every other user of that list:

BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x1aa/0x1c0 Read of size 8 at addr ffff888153c6a418 by task poc_corr/486 Call Trace: __list_add_valid_or_report+0x1aa/0x1c0 ucma_event_handler+0x1be/0xc00 ucma_set_ib_path+0x45e/0x710 ucma_set_option+0x32e/0x590 ucma_write+0x1f9/0x330 Allocated by task 505: ucma_write_cm_event+0x1a1/0x660 Freed by task 505: kfree+0x1da/0x4c0 ucma_get_event+0x5d5/0x7e0

The freed object is a ucma_event that another thread dequeued from file B's list under file B's mutex. File A's mut is left held on top of that, wedging its next writer in uninterruptible sleep.

This path needs a bound and address-resolved cm_id, so it requires an RDMA device to be present.

Take the handler lock around the call.

CVSS Base Scores

version 3.1