CVE-2026-90183
UnknownSummary
In the Linux kernel's blk-iolatency mechanism, delay state is not cleared when freeing policy data. A blk-cgroup can remain permanently marked as congested, causing readahead to be cut and throttling to be scheduled on anonymous folio allocation.
Risk Assessment
All tasks in the affected cgroup and its descendants may experience persistent I/O slowdown and memory allocation delays. This can degrade the performance of applications running in that group.
Recommendation
Update the kernel to a version containing the fix that clears the delay state in iolatency_pd_free(). Until then, monitor cgroups for sustained congestion.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: blk-iolatency: clear delay state when freeing policy data io.latency can throttle a group which has no latency target of its own. When a sibling misses its target, check_scale_change() scales down its peers, and a peer that reaches queue depth one gets blkcg_use_delay() called on it on every further scale-down, even with min_lat_nsec == 0. iolatency_pd_offline() resets the target through iolatency_set_min_lat_nsec(), which clears the delay only on a nonzero to zero transition, so it never clears such a peer. Freeing the policy data then leaves blkg->use_delay set and blkcg->congestion_count elevated with nothing left that can drop it. blk_cgroup_congested() then returns true for every task in that cgroup and its descendants for as long as the cgroup lives: page_cache_sync_ra() cuts readahead to a single page, page_cache_async_ra() skips it altogether, and __folio_throttle_swaprate() takes swap_avail_lock and schedules a throttle on anonymous folio allocation. Clear the delay in iolatency_pd_free(). By then bio-held blkg references have drained, or the queue is frozen for policy deactivation, so check_scale_change() cannot re-arm it. The free callback can also see policy data which was never attached to a blkg, hence the pd->blkg check.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS