CVE-2026-89955
UnknownSummary
In the Linux kernel, vfio_ap_mdev_probe_queue() created the sysfs attribute group before the queue's driver data was set. A concurrent read of the 'status' attribute could call dev_get_drvdata() and get NULL, which was then dereferenced in vfio_ap_mdev_for_queue(), causing a NULL pointer dereference.
Risk Assessment
A NULL pointer dereference in the kernel during a concurrent sysfs attribute read can cause a system crash (panic) or denial of service.
Recommendation
Update the Linux kernel to a version containing the fix that acquires the update locks before sysfs_create_group() and reads the APQN from apdev before allocation.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: s390/vfio-ap: Fix NULL deref in status_show() during queue probe When vfio_ap_mdev_probe_queue() creates the sysfs attribute group, the queue's driver data has not yet been set. A concurrent read of the 'status' attribute can therefore call dev_get_drvdata() and get NULL, which is then passed directly to vfio_ap_mdev_for_queue() where q->apqn is unconditionally dereferenced, causing a NULL pointer dereference. Fix this by acquiring the update locks before calling sysfs_create_group(). The status_show() function acquires guests_lock before reading the driver data, so any concurrent read will block until after dev_set_drvdata() has been called and the update locks are released. As a bonus, the APQN no longer needs to be read from the queue struct after allocation — it can be read directly from apdev before allocation and stored in a local variable, which is then assigned to q->apqn once the allocation succeeds.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS