Bug 2350581 (CVE-2025-21840)

Summary: CVE-2025-21840 kernel: thermal/netlink: Prevent userspace segmentation fault by adjusting UAPI header
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-03-07 10:01:00 UTC
In the Linux kernel, the following vulnerability has been resolved:

thermal/netlink: Prevent userspace segmentation fault by adjusting UAPI header

The intel-lpmd tool [1], which uses the THERMAL_GENL_ATTR_CPU_CAPABILITY
attribute to receive HFI events from kernel space, encounters a
segmentation fault after commit 1773572863c4 ("thermal: netlink: Add the
commands and the events for the thresholds").

The issue arises because the THERMAL_GENL_ATTR_CPU_CAPABILITY raw value
was changed while intel_lpmd still uses the old value.

Although intel_lpmd can be updated to check the THERMAL_GENL_VERSION and
use the appropriate THERMAL_GENL_ATTR_CPU_CAPABILITY value, the commit
itself is questionable.

The commit introduced a new element in the middle of enum thermal_genl_attr,
which affects many existing attributes and introduces potential risks
and unnecessary maintenance burdens for userspace thermal netlink event
users.

Solve the issue by moving the newly introduced
THERMAL_GENL_ATTR_TZ_PREV_TEMP attribute to the end of the
enum thermal_genl_attr. This ensures that all existing thermal generic
netlink attributes remain unaffected.

[ rjw: Subject edits ]