CVE-2025-39999

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

blk-mq: fix blk_mq_tags double free while nr_requests grown

In the case user trigger tags grow by queue sysfs attribute nr_requests, hctx->sched_tags will be freed directly and replaced with a new allocated tags, see blk_mq_tag_update_depth().

The problem is that hctx->sched_tags is from elevator->et->tags, while et->tags is still the freed tags, hence later elevator exit will try to free the tags again, causing kernel panic.

Fix this problem by replacing et->tags with new allocated tags as well.

Noted there are still some long term problems that will require some refactor to be fixed thoroughly[1].

[1] https://lore.kernel.org/all/[email protected]/

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.