Linux Kernel up to 7.2.5 blk-iolatency iolatency_pd_free use_delay/congestion_count denial of service

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 7.2.5. The impacted element is the function iolatency_pd_free of the component blk-iolatency. The manipulation of the argument use_delay/congestion_count results in denial of service. This vulnerability is known as CVE-2026-90183. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 7.2.5. Affected is the function iolatency_pd_free of the component blk-iolatency. The manipulation of the argument use_delay/congestion_count with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2026-90183 since 09/11/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/17/2026). This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch 8935bf22c0a0db517a7f72f7097300e05dd852f5 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5

License

• open-source

Website

• Vendor: https://www.kernel.org/

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