Description
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_tcm: keep port count until LUN teardown completes
tcm_usbg_drop_nexus() permits session removal once tpg_port_count
reaches zero. However, usbg_port_unlink() currently decrements that
count from the fabric_pre_unlink() callback, before core_dev_del_lun()
waits for active se_lun references to drain.
If removal of the last LUN races a nexus removal, the latter can observe
a zero port count and call target_remove_session(). This frees
sess_cmd_map while an in-flight struct usbg_cmd, including its work item,
can still be accessed.
Overlapping the last-LUN unlink with nexus removal reproduces this
lifetime violation as a DEBUG_OBJECTS "free active" warning for
usbg_cmd_work, followed by a target-core BUG/Oops.
The generic target-core unlink path has no callback after
core_dev_del_lun() completes. Add an optional fabric_post_unlink()
callback and use it for the f_tcm port count. The count now remains
nonzero until core_dev_del_lun() has finished draining active LUN
references, preventing nexus removal from freeing the session during
command completion.
usb: gadget: f_tcm: keep port count until LUN teardown completes
tcm_usbg_drop_nexus() permits session removal once tpg_port_count
reaches zero. However, usbg_port_unlink() currently decrements that
count from the fabric_pre_unlink() callback, before core_dev_del_lun()
waits for active se_lun references to drain.
If removal of the last LUN races a nexus removal, the latter can observe
a zero port count and call target_remove_session(). This frees
sess_cmd_map while an in-flight struct usbg_cmd, including its work item,
can still be accessed.
Overlapping the last-LUN unlink with nexus removal reproduces this
lifetime violation as a DEBUG_OBJECTS "free active" warning for
usbg_cmd_work, followed by a target-core BUG/Oops.
The generic target-core unlink path has no callback after
core_dev_del_lun() completes. Add an optional fabric_post_unlink()
callback and use it for the f_tcm port count. The count now remains
nonzero until core_dev_del_lun() has finished draining active LUN
references, preventing nexus removal from freeing the session during
command completion.
Published:
2026-09-04
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
No advisories yet.
References
History
Fri, 04 Sep 2026 16:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_tcm: keep port count until LUN teardown completes tcm_usbg_drop_nexus() permits session removal once tpg_port_count reaches zero. However, usbg_port_unlink() currently decrements that count from the fabric_pre_unlink() callback, before core_dev_del_lun() waits for active se_lun references to drain. If removal of the last LUN races a nexus removal, the latter can observe a zero port count and call target_remove_session(). This frees sess_cmd_map while an in-flight struct usbg_cmd, including its work item, can still be accessed. Overlapping the last-LUN unlink with nexus removal reproduces this lifetime violation as a DEBUG_OBJECTS "free active" warning for usbg_cmd_work, followed by a target-core BUG/Oops. The generic target-core unlink path has no callback after core_dev_del_lun() completes. Add an optional fabric_post_unlink() callback and use it for the f_tcm port count. The count now remains nonzero until core_dev_del_lun() has finished draining active LUN references, preventing nexus removal from freeing the session during command completion. | |
| Title | usb: gadget: f_tcm: keep port count until LUN teardown completes | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-04T15:55:06.478Z
Reserved: 2026-08-26T14:34:25.797Z
Link: CVE-2026-80854
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-04T16:18:14.353
Modified: 2026-09-04T16:18:14.353
Link: CVE-2026-80854
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.