Description
In the Linux kernel, the following vulnerability has been resolved:

scsi: target: Disable interrupts while holding delayed_cmd_lock

target_do_delayed_work() takes dev->delayed_cmd_lock with a plain
spin_lock(). It runs from system_percpu_wq, so interrupts stay enabled
while the lock is held. Every other acquisition of that lock uses
spin_lock_irqsave(): target_handle_task_attr() and
transport_complete_ordered_sync() in target_core_transport.c, and
target_non_ordered_release() in target_core_device.c.

That was safe while every caller of transport_complete_task_attr() ran
in process context: target_complete_ok_work() from target_completion_wq,
transport_complete_qf() from dev->qf_work_queue, and
transport_generic_request_failure() from the submit and execute paths.

Since commit 06933066d88a ("scsi: target: Add support for completing
commands from backend context") that is no longer true. With
complete_type=1 on a fabric that sets direct_compl_supp,
target_complete() runs target_complete_ok_work() inline in the backend's
completion context, which target_complete_cmd_with_sense() documents as
"May be called from interrupt context". For iblock that is the bio
end_io.

target_complete_ok_work() starts with transport_complete_task_attr(),
which takes delayed_cmd_lock in two ways:

- Every ORDERED command is put on dev->delayed_cmd_list by
target_handle_task_attr() and dispatched from there by
target_do_delayed_work(), which marks it SCF_TASK_ORDERED_SYNC. Its
completion therefore goes through transport_complete_ordered_sync().

- A SIMPLE command that completes while an ORDERED command is pending
drops the last reference to the killed dev->non_ordered, and
percpu_ref_put() then runs target_non_ordered_release() in the
completing context.

Both take the lock and, if commands are waiting, call
schedule_work(&dev->delayed_cmd_work), which queues on system_percpu_wq,
i.e. on the CPU that took the completion. Further completions for the
same queue are typically delivered there too, so one arriving while the
work holds the lock spins on it forever.

Reaching this needs complete_type=1, which is not the default
(vhost-scsi, the only fabric with direct_compl_supp, defaults to
TARGET_QUEUE_COMPL), a backend whose I/O completes from interrupt
context, and ORDERED commands from the initiator. Linux virtio_scsi
guests send only VIRTIO_SCSI_S_SIMPLE and never take the ordered path;
any guest that uses the ORDERED task attribute, which vhost-scsi
accepts, does.

target_do_delayed_work() is a work item and always runs in process
context, so spin_lock_irq() is sufficient.

Found by inspection; no runtime report. A single ORDERED command goes
through both acquisitions, so with CONFIG_PROVE_LOCKING the first one
completed through direct completion should produce an inconsistent lock
state report on delayed_cmd_lock (hardirq or softirq, depending on where
the backend completes).
Published: 2026-10-28
Score: n/a
EPSS: n/a
KEV: No
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Remediation

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History

Wed, 28 Oct 2026 17:00:00 +0000

Type Values Removed Values Added
First Time appeared Linux linux
Vendors & Products Linux linux

Wed, 28 Oct 2026 12:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-663

Wed, 28 Oct 2026 10:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: scsi: target: Disable interrupts while holding delayed_cmd_lock target_do_delayed_work() takes dev->delayed_cmd_lock with a plain spin_lock(). It runs from system_percpu_wq, so interrupts stay enabled while the lock is held. Every other acquisition of that lock uses spin_lock_irqsave(): target_handle_task_attr() and transport_complete_ordered_sync() in target_core_transport.c, and target_non_ordered_release() in target_core_device.c. That was safe while every caller of transport_complete_task_attr() ran in process context: target_complete_ok_work() from target_completion_wq, transport_complete_qf() from dev->qf_work_queue, and transport_generic_request_failure() from the submit and execute paths. Since commit 06933066d88a ("scsi: target: Add support for completing commands from backend context") that is no longer true. With complete_type=1 on a fabric that sets direct_compl_supp, target_complete() runs target_complete_ok_work() inline in the backend's completion context, which target_complete_cmd_with_sense() documents as "May be called from interrupt context". For iblock that is the bio end_io. target_complete_ok_work() starts with transport_complete_task_attr(), which takes delayed_cmd_lock in two ways: - Every ORDERED command is put on dev->delayed_cmd_list by target_handle_task_attr() and dispatched from there by target_do_delayed_work(), which marks it SCF_TASK_ORDERED_SYNC. Its completion therefore goes through transport_complete_ordered_sync(). - A SIMPLE command that completes while an ORDERED command is pending drops the last reference to the killed dev->non_ordered, and percpu_ref_put() then runs target_non_ordered_release() in the completing context. Both take the lock and, if commands are waiting, call schedule_work(&dev->delayed_cmd_work), which queues on system_percpu_wq, i.e. on the CPU that took the completion. Further completions for the same queue are typically delivered there too, so one arriving while the work holds the lock spins on it forever. Reaching this needs complete_type=1, which is not the default (vhost-scsi, the only fabric with direct_compl_supp, defaults to TARGET_QUEUE_COMPL), a backend whose I/O completes from interrupt context, and ORDERED commands from the initiator. Linux virtio_scsi guests send only VIRTIO_SCSI_S_SIMPLE and never take the ordered path; any guest that uses the ORDERED task attribute, which vhost-scsi accepts, does. target_do_delayed_work() is a work item and always runs in process context, so spin_lock_irq() is sufficient. Found by inspection; no runtime report. A single ORDERED command goes through both acquisitions, so with CONFIG_PROVE_LOCKING the first one completed through direct completion should produce an inconsistent lock state report on delayed_cmd_lock (hardirq or softirq, depending on where the backend completes).
Title scsi: target: Disable interrupts while holding delayed_cmd_lock
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-28T10:36:00.728Z

Reserved: 2026-09-25T10:25:14.401Z

Link: CVE-2026-99207

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-28T11:17:42.033

Modified: 2026-10-28T11:17:42.033

Link: CVE-2026-99207

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-28T16:45:04Z

Weaknesses
  • CWE-663

    Use of a Non-reentrant Function in a Concurrent Context