CVE-2026-89956s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects
- —Not scoredno CVSS score yet
- 0.23%Exploitation in 30 daysEPSS · top 86% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects In order to traverse or add/remove ap_matrix_mdev objects in the matrix_dev->mdev_list, the matrix_dev->guests_lock mutex must be held. There are two functions that access the list without holding the mutex: vfio_ap_mdev_probe function ~~~~~~~~~~~~~~~~~~~~~~~~~~~ The vfio_ap_mdev_probe function uses the matrix_dev->mdevs_lock mutex to guard the add of a newly created ap_matrix_mdev object to the matrix_dev->mdev_list. This mutex does not protect list access; its purpose is to guard against concurrent access to fields contained in an ap_matrix_mdev object. This could lead to kernel memory corruption or use-after-free if another mdev is created or removed concurrently. The adding of an ap_matrix_mdev object to matrix_dev->mdev_list is now guarded by the matrix_dev->guests_lock which is the correct way to protect against concurrent mdev_list access. Also removed the following two lines of code because the matrix_mdev is allocated via vfio_alloc_device macro which uses kzalloc, so req_trigger and cfg_chg_trigger are already zero-initialised when the struct is allocated before the call to vfio_register_emulated_iommu_dev. This prevents a window whereby these triggers are set to NULL after the device is exposed to userspace. matrix_mdev->req_trigger = NULL; matrix_mdev->cfg_chg_trigger = NULL; vfio_ap_mdev_for_queue function ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The status_show function that supports display of the status attribute of the devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue function which iterates the matrix_dev->mdev_list to find the object representing the queue device whose status is to be displayed. In order to traverse this list, the matrix_dev->guests_lock mutex must be held. To fix this, the guests_lock mutex is taken prior to taking the matrix_dev->mdevs_lock mutex in the status_show function. It is taken there rather than the vfio_ap_mdev_for_queue function - where it is needed - because it must be taken prior to the mdevs_lock mutex in order to adhere to the proper locking order and prevent a lockdep splat; also because the mdevs_lock is needed there to access fields within the matrix_mdev object in that function. See the vfio-ap-locking.rst in the linux kernel tree.
Timeline
ID reserved
By Linux
- 5 days later
· 5 days later
Published
- 44 days later
· 44 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.
- EPSS (exploitation in 30 days)
- 0.23% · top 86% of all CVEs (14 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.
Affected products
- affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a – < 3ea443510739468238324234eaab0d37922283f5
- affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a – < 22dc712c170efc1a549e3f872467c880be995ac7
- affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a – < 530ee1cc71562b6799b9ece187b6c1b757a2c6fa
- affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a – < 647916988272fe5ecb4bb30cd02b51af9960618a
- affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a – < 0fd74477d05743d4cd9b25a3b667daa278d53b93
- affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a – < 7fa61c29850d05e40ca9ed41bfdf57673023f581
- affected 6.0
- unaffected < 6.0
- unaffected 6.1.191 – ≤ 6.1.*
- unaffected 6.6.160 – ≤ 6.6.*
- unaffected 6.12.112 – ≤ 6.12.*
- unaffected 6.18.51 – ≤ 6.18.*
- unaffected 7.2.5 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References6
- https://git.kernel.org/stable/c/3ea443510739468238324234eaab0d37922283f5 (opens in a new tab)
- https://git.kernel.org/stable/c/22dc712c170efc1a549e3f872467c880be995ac7 (opens in a new tab)
- https://git.kernel.org/stable/c/530ee1cc71562b6799b9ece187b6c1b757a2c6fa (opens in a new tab)
- https://git.kernel.org/stable/c/647916988272fe5ecb4bb30cd02b51af9960618a (opens in a new tab)
- https://git.kernel.org/stable/c/0fd74477d05743d4cd9b25a3b667daa278d53b93 (opens in a new tab)
- https://git.kernel.org/stable/c/7fa61c29850d05e40ca9ed41bfdf57673023f581 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-80556 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-89956)Record last updated .