CVE-2026-89956— s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
以下是该漏洞描述的中文翻译： 在 Linux 内核中，以下漏洞已得到修复： s390/vfio-ap：修复访问 ap_matrix_mdev 对象列表时缺失的锁 为了遍历或在 中添加/移除 对象，必须持有 互斥锁。然而，有两个函数在访问该列表时并未持有此互斥锁： vfio_ap_mdev_probe 函数 函数使用 互斥锁来保护新创建的 对象添加到 的过程。但该互斥锁并不保护列表本身的访问；它的目的是防止对 对象内部字段的并发访问。如果在并发地创建或移除另一个 mdev 时未正确加锁，可能会导致内核内存损坏或释放后
Possible ATT&CK Techniques 1 AI
T1069 · Permission Groups DiscoveryAffected Version Matrix 10
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a< 530ee1cc71562b6799b9ece187b6c1b757a2c6fa |
affected |
2c1ee8983aa377fef4f725162f4f3aa5f9575d4a< 647916988272fe5ecb4bb30cd02b51af9960618a |
affected | ||
2c1ee8983aa377fef4f725162f4f3aa5f9575d4a< 0fd74477d05743d4cd9b25a3b667daa278d53b93 |
affected | ||
2c1ee8983aa377fef4f725162f4f3aa5f9575d4a< 7fa61c29850d05e40ca9ed41bfdf57673023f581 |
affected | ||
6.0 |
affected | ||
< 6.0 |
unaffected | ||
6.12.112≤ 6.12.* |
unaffected | ||
6.18.51≤ 6.18.* |
unaffected | ||
| … +2 more rows | |||
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I. Basic Information for CVE-2026-89956
Vulnerability Information
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Vulnerability Title
s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-89956
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|---|
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Patches & Fixes for CVE-2026-89956 (1)
Other References for CVE-2026-89956 (3)
Same Patch Batch · Linux · 2026-09-16 · 276 CVEs total
| CVE-2026-90048 | 9.8 CRITICAL | fs/ntfs3: fix slab-out-of-bounds write in ni_create_attr_list() |
| CVE-2026-90012 | 9.8 CRITICAL | spi: Fix DMA mapping ownership on partial map failure |
| CVE-2026-89970 | 9.8 CRITICAL | nvmet-auth: Synchronize timeout work during SQ teardown |
| CVE-2026-89857 | 9.8 CRITICAL | scsi: qla2xxx: Hold qpair lock when sending NVMe LS reject |
| CVE-2026-89969 | 9.8 CRITICAL | nvmet-tcp: fix out-of-bounds write when receiving an over-long PDU |
| CVE-2026-89847 | 9.8 CRITICAL | scsi: qla2xxx: Avoid double completion in async IOCB timeout |
| CVE-2026-89972 | 9.8 CRITICAL | nvme: add missing SRCU grace period in error path |
| CVE-2026-89990 | 9.8 CRITICAL | ceph: lock mutex in ceph_mds_check_access() |
| CVE-2026-90036 | 9.8 CRITICAL | NFSD: Prevent client use-after-free during blocked-lock reaping |
| CVE-2026-90038 | 9.8 CRITICAL | NFSD: Prevent client use-after-free during export state revocation |
| CVE-2026-90037 | 9.8 CRITICAL | NFSD: Prevent client use-after-free during close_lru reaping |
| CVE-2026-89788 | 9.8 CRITICAL | ksmbd: fix tree connection use-after-free in smb2_tree_connect() |
| CVE-2026-89783 | 9.8 CRITICAL | xfrm6: fix out-of-bounds write in xfrm6_input_addr() when secpath is full |
| CVE-2026-90042 | 9.8 CRITICAL | ceph: properly decrypt filenames in vmalloc() buffers |
| CVE-2026-89778 | 9.8 CRITICAL | isofs: fix out-of-bounds page array access on empty zisofs block |
| CVE-2026-89915 | 9.3 CRITICAL | KVM: arm64: Remove VM-wide VNCR mapping counter |
| CVE-2026-90049 | 9.3 CRITICAL | net: skbuff: don't skb_tx_error() the source skb in skb_zerocopy() |
| CVE-2026-89775 | 9.3 CRITICAL | KVM: arm64: Handle negative S1 walk levels in VNCR TLB size evaluation |
| CVE-2026-89916 | 9.3 CRITICAL | KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry |
| CVE-2026-89930 | 9.3 CRITICAL | KVM: nVMX: Service local TLB flushes on failed nested VM-Enter |
Showing top 20 of 276 CVEs. View all on vendor page → →
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