# CVE-2025-68807: linux: In the Linux kernel, the following vulnerability has been resolved:  block: fix race between wbt_enable_default and I...

CVE-2025-68807 is fixed in linux on 1 platform by DEBIAN-CVE-2025-68807 (version 6.18.3-1), released January 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-68807
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jan 13, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  block: fix race between wbt_enable_default and IO submission  When wbt_enable_default() is moved out of queue freezing in elevator_change(), it can cause the wbt inflight counter to become negative (-1), leading to hung tasks in the writeback path. Tasks get stuck in wbt_wait() because the counter is in an inconsistent state.  The issue occurs because wbt_enable_default() could race with IO submission, allowing the counter to be decremented before proper initialization. This manifests as:    rq_wait[0]:     inflight:             -1     has_waiters:        True  rwb_enabled() checks the state, which can be updated exactly between wbt_wait() (rq_qos_throttle()) and wbt_track()(rq_qos_track()), then the inflight counter will become negative.  And results in hung task warnings like:   task:kworker/u24:39 state:D stack:0 pid:14767   Call Trace:     rq_qos_wait+0xb4/0x150     wbt_wait+0xa9/0x100     __rq_qos_throttle+0x24/0x40     blk_mq_submit_bio+0x672/0x7b0     ...  Fix this by:  1. Splitting wbt_enable_default() into:    - __wbt_enable_default(): Returns true if wbt_init() should be called    - wbt_enable_default(): Wrapper for existing callers (no init)    - wbt_init_enable_default(): New function that checks and inits WBT  2. Using wbt_init_enable_default() in blk_register_queue() to ensure    proper initialization during queue registration  3. Move wbt_init() out of wbt_enable_default() which is only for enabling    disabled wbt from bfq and iocost, and wbt_init() isn't needed. Then the    original lock warning can be avoided.  4. Removing the ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT flag and its handling    code since it's no longer needed  This ensures WBT is properly initialized before any IO can be submitted, preventing the counter from going negative.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 6.18.3-1 | [DEBIAN-CVE-2025-68807](https://patchblox.com/security/data/fix/linux/debian-cve-2025-68807.md) | Jan 13, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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