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.
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.
Metrics
Affected Vendors & Products
Advisories
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | blk-iolatency: clear delay state when freeing policy data | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:07:07.045Z
Reserved: 2026-09-11T19:38:34.791Z
Link: CVE-2026-90183
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:12.710
Modified: 2026-09-17T17:17:12.710
Link: CVE-2026-90183
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.