CVE-2025-39999
Severity CVSS v4.0:
Pending analysis
Type:
Unavailable / Other
Publication date:
15/10/2025
Last modified:
16/10/2025
Description
In the Linux kernel, the following vulnerability has been resolved:<br />
<br />
blk-mq: fix blk_mq_tags double free while nr_requests grown<br />
<br />
In the case user trigger tags grow by queue sysfs attribute nr_requests,<br />
hctx->sched_tags will be freed directly and replaced with a new<br />
allocated tags, see blk_mq_tag_update_depth().<br />
<br />
The problem is that hctx->sched_tags is from elevator->et->tags, while<br />
et->tags is still the freed tags, hence later elevator exit will try to<br />
free the tags again, causing kernel panic.<br />
<br />
Fix this problem by replacing et->tags with new allocated tags as well.<br />
<br />
Noted there are still some long term problems that will require some<br />
refactor to be fixed thoroughly[1].<br />
<br />
[1] https://lore.kernel.org/all/20250815080216.410665-1-yukuai1@huaweicloud.com/