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CVE-2025-68756

In the Linux kernel, the following vulnerability has been resolved: block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock blk_mq_{add,del}_queue_…

Published Jan 5, 2026 · updated Oct 14, 2026

In the Linux kernel, the following vulnerability has been resolved: block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock blk_mq_{add,del}_queue_tag_set() functions add and remove queues from tagset, the functions make sure that tagset and queues are marked as shared when two or more queues are attached to the same tagset. Initially a tagset starts as unshared and when the number of added queues reaches two, blk_mq_add_queue_tag_set() marks it as shared along with all the queues attached to it. When the number of attached queues drops to 1 blk_mq_del_queue_tag_set() need to mark both the tagset and the remaining queues as unshared. Both functions need to freeze current queues in tagset before setting on unsetting BLK_MQ_F_TAG_QUEUE_SHARED flag. While doing so, both functions hold set->tag_list_lock mutex, which makes sense as we do not want queues to be added or deleted in the process. This used to work fine until commit 98d81f0df70c ("nvme: use blk_mq_[un]quiesce_tagset") made the nvme driver quiesce tagset instead of quiscing individual queues. blk_mq_quiesce_tagset() does the job and quiesce the queues in set->tag_list while holding set->tag_list_lock also. This results in deadlock between two threads with these stacktraces: __schedule+0x47c/0xbb0 ? timerqueue_add+0x66/0xb0 schedule+0x1c/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.constprop.0+0x271/0x600 blk_mq_quiesce_tagset+0x25/0xc0 nvme_dev_disable+0x9c/0x250 nvme_timeout+0x1fc/0x520 blk_mq_handle_expired+0x5c/0x90 bt_iter+0x7e/0x90 blk_mq_queue_tag_busy_iter+0x27e/0x550 ? __blk_mq_complete_request_remote+0x10/0x10 ? __blk_mq_complete_request_remote+0x10/0x10 ? __call_rcu_common.constprop.0+0x1c0/0x210 blk_mq_timeout_work+0x12d/0x170 process_one_work+0x12e/0x2d0 worker_thread+0x288/0x3a0 ? rescuer_thread+0x480/0x480 kthread+0xb8/0xe0 ? kthread_park+0x80/0x80 ret_from_fork+0x2d/0x50 ? kthread_park+0x80/0x80 ret_from_fork_asm+0x11/0x20 __schedule+0x47c/0xbb0 ? xas_find+0x161/0x1a0

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jan 5, 2026 · NIST NVD

    Detected

    In the Linux kernel, the following vulnerability has been resolved: block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock blk_mq_{add,del}_queue_tag_set() functions add and remove queues from tagset, the functions make sure that tagset and queues are marked as shared when two or more queues are attached to the same tagset. Initially a tagset starts as unshared and when the nu

  2. Oct 14, 2026 · NIST NVD

    Updated

    In the Linux kernel, the following vulnerability has been resolved: block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock blk_mq_{add,del}_queue_tag_set() functions add and remove queues from tagset, the functions make sure that tagset and queues are marked as shared when two or more queues are attached to the same tagset. Initially a tagset starts as unshared and when the nu

Sources

  • CVE.orgVulnerability recordCVE-2025-68756

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-68756

    30-day exploitation probability 0.2%

    first.org
  • NIST NVDVulnerability recordCVE-2025-68756

    In the Linux kernel, the following vulnerability has been resolved: block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock blk_mq_{add,del}_queue_tag_set() functions add and remove queues from tagset, the functions make sure that tagset and queues are marke

    nvd.nist.gov

References