Bug 2363672 (CVE-2025-37797)

Summary:	CVE-2025-37797 kernel: net_sched: hfsc: Fix a UAF vulnerability in class handling
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, vkumar
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-05-02 15:01:22 UTC

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

net_sched: hfsc: Fix a UAF vulnerability in class handling

This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class
handling. The issue occurs due to a time-of-check/time-of-use condition
in hfsc_change_class() when working with certain child qdiscs like netem
or codel.

The vulnerability works as follows:
1. hfsc_change_class() checks if a class has packets (q.qlen != 0)
2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g.,
   codel, netem) might drop packets and empty the queue
3. The code continues assuming the queue is still non-empty, adding
   the class to vttree
4. This breaks HFSC scheduler assumptions that only non-empty classes
   are in vttree
5. Later, when the class is destroyed, this can lead to a Use-After-Free

The fix adds a second queue length check after qdisc_peek_len() to verify
the queue wasn't emptied.

Comment 1 Avinash Hanwate 2025-05-05 06:08:10 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025050210-CVE-2025-37797-2aab@gregkh/T

Comment 5 errata-xmlrpc 2025-07-28 08:23:49 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2025:11855 https://access.redhat.com/errata/RHSA-2025:11855

Comment 6 errata-xmlrpc 2025-07-28 10:05:03 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2025:11861 https://access.redhat.com/errata/RHSA-2025:11861

Comment 7 errata-xmlrpc 2025-08-11 14:17:57 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2025:13633 https://access.redhat.com/errata/RHSA-2025:13633

Comment 8 errata-xmlrpc 2025-08-13 09:36:31 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2025:13781 https://access.redhat.com/errata/RHSA-2025:13781

Comment 9 errata-xmlrpc 2025-08-18 01:38:46 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Extended Update Support

Via RHSA-2025:13946 https://access.redhat.com/errata/RHSA-2025:13946

Comment 10 errata-xmlrpc 2025-08-19 00:18:31 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions

Via RHSA-2025:14054 https://access.redhat.com/errata/RHSA-2025:14054

Comment 14 errata-xmlrpc 2025-08-19 13:16:51 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions

Via RHSA-2025:14094 https://access.redhat.com/errata/RHSA-2025:14094

Comment 15 errata-xmlrpc 2025-09-29 10:19:05 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2025:16920 https://access.redhat.com/errata/RHSA-2025:16920

Comment 16 errata-xmlrpc 2025-09-29 12:10:04 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2025:16919 https://access.redhat.com/errata/RHSA-2025:16919

Comment 19 errata-xmlrpc 2025-10-22 00:23:09 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2025:18932 https://access.redhat.com/errata/RHSA-2025:18932

Comment 20 errata-xmlrpc 2025-10-29 00:36:07 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.6 Telecommunications Update Service

Via RHSA-2025:19222 https://access.redhat.com/errata/RHSA-2025:19222