ublk: wait on ublk_dev_ready() instead of ub->completion

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-68173
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-10 13:20:04 UTC
Updated2026-08-10 13:20:04 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ublk: wait on ublk_dev_ready() instead of ub->completion ub->completion is only re-armed by a successful START_USER_RECOVERY. If the ublk server sends END_USER_RECOVERY without one - e.g. its START failed with -EBUSY and the error was ignored - the wait is satisfied by the stale completion of the previous recovery cycle, and the device is marked LIVE and the requeue list kicked while the FETCH stream is still running and ubq->canceling is still set. The kick redispatches a previously requeued request, __ublk_queue_rq_common() sees ->canceling and parks it again via __ublk_abort_rq(), and after the last FETCH clears ->canceling nothing ever kicks the requeue list again: the request is stranded there while holding its tag. If it is the flush machinery's flush_rq, every subsequent fsync piles up in uninterruptible sleep and teardown hangs on tag draining. This matches a report of a lost PREFLUSH with ext4 on top of ublk after daemon crash recovery. ub->completion is an edge-triggered latch used as a proxy for the level condition "every queue has fetched all I/O commands", which can regress (F_BATCH's UNPREP, daemon death) and whose re-arm can be skipped. Drop it and wait on the real condition instead: the new helper ublk_wait_dev_ready_and_lock() waits on ublk_dev_ready() via wait_var_event_interruptible(), woken from ublk_mark_io_ready(), then re-checks it under ub->mutex, waiting again on regression, and returns with the mutex held and readiness guaranteed. Readiness becomes true in the same ub->mutex critical section that clears the last queue's ->canceling, so END_USER_RECOVERY marks the device LIVE and kicks the requeue list strictly after ->canceling clears. The wait stays interruptible, so a server whose daemon died can still be signalled out. For ublk_ctrl_start_dev() this replaces the fail-fast -EINVAL on an F_BATCH ready->UNPREP regression with waiting until the device is ready again.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b 7dd26adf7e7d482af524e3a0cca4a81ef7c159d0 git Not specified
CNA Linux Linux affected 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b 8f188dd11a1c2ad94caeaee36ef68bb8221d4a12 git Not specified
CNA Linux Linux affected 728cbac5fe219d3b8a21a0688a08f2b7f8aeda2b 432a9b2780c0a01caf547bd1fc2fcf28aeb8d173 git Not specified
CNA Linux Linux affected 42ea64e01c96e594fb4f80c54dfe4f934d008a6e git Not specified
CNA Linux Linux affected 6.14.6 6.15 semver Not specified
CNA Linux Linux affected 6.15 Not specified
CNA Linux Linux unaffected 6.15 semver Not specified
CNA Linux Linux unaffected 6.18.42 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.6 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc5 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/432a9b2780c0a01caf547bd1fc2fcf28aeb8d173 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8f188dd11a1c2ad94caeaee36ef68bb8221d4a12 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7dd26adf7e7d482af524e3a0cca4a81ef7c159d0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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