CVE-2026-90325

About vulnerability

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

blk-cgroup: skip dying blkg in blkcg_activate_policy()

When switching IO schedulers on a block device, blkcg_activate_policy() can race with concurrent blkcg deletion, leading to a use-after-free in rcu_accelerate_cbs.

T1: T2: blkg_destroy kill(&blkg->refcnt) // blkg->refcnt=1->0 blkg_release // call_rcu(__blkg_release) … blkg_free_workfn ->pd_free_fn(pd) elv_iosched_store elevator_switch … iterate blkg list blkg_get(blkg) // blkg->refcnt=0->1 list_del_init(&blkg->q_node) blkg_put(pinned_blkg) // blkg->refcnt=1->0 blkg_release // call_rcu again rcu_accelerate_cbs // uaf

Fix this by checking hlist_unhashed(&blkg->blkcg_node) before getting a reference to the blkg. This is the same check used in blkg_destroy() to detect if a blkg has already been destroyed. If the blkg is already unhashed, skip processing it since it’s being destroyed.

Affected product:

AlmaLinux 9.2 ESU , TuxCare 9.6 ESU , TuxCare 9.8 ESU

Affected packages:

kernel @ 5.14.0 (+2 more)

Live-patch status from KernelCare for each operating system.