CVE-2026-22995

Summary

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

ublk: fix use-after-free in ublk_partition_scan_work

A race condition exists between the async partition scan work and device teardown that can lead to a use-after-free of ub->ub_disk:

1. ublk_ctrl_start_dev() schedules partition_scan_work after add_disk()
2. ublk_stop_dev() calls ublk_stop_dev_unlocked() which does:
   • del_gendisk(ub->ub_disk)
   • ublk_detach_disk() sets ub->ub_disk = NULL
   • put_disk() which may free the disk
3. The worker ublk_partition_scan_work() then dereferences ub->ub_disk leading to UAF

Fix this by using ublk_get_disk()/ublk_put_disk() in the worker to hold a reference to the disk during the partition scan. The spinlock in ublk_get_disk() synchronizes with ublk_detach_disk() ensuring the worker either gets a valid reference or sees NULL and exits early.

Also change flush_work() to cancel_work_sync() to avoid running the partition scan work unnecessarily when the disk is already detached.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/72e28774e9644c2bdbb4920842fbf77103a15a85
• https://git.kernel.org/stable/c/f0d385f6689f37a2828c686fb279121df006b4cb

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