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CVE-2025-38457

net/sched: Abort __tc_modify_qdisc if parent class does not exist

MEDIUM 5.5

At a glance

Source
NVD
EPSS
EPSS 0.20 % · percentile 9 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: Abort __tc_modify_qdisc if parent class does not exist Lion's patch [1] revealed an ancient bug in the qdisc API. Whenever a user creates/modifies a qdisc specifying as a parent another qdisc, the qdisc API will, during grafting, detect that the user is not trying to attach to a class and reject. However grafting is performed after qdisc_create (and thus the qdiscs' init callback) is executed. In qdiscs that eventually call qdisc_tree_reduce_backlog during init or change (such as fq, hhf, choke, etc), an issue arises. For example, executing the following commands: sudo tc qdisc add dev lo root handle a: htb default 2 sudo tc qdisc add dev lo parent a: handle beef fq Qdiscs such as fq, hhf, choke, etc unconditionally invoke qdisc_tree_reduce_backlog() in their control path init() or change() which then causes a failure to find the child class; however, that does not stop the unconditional invocation of the assumed child qdisc's qlen_notify with a null class. All these qdiscs make the assumption that class is non-null. The solution is ensure that qdisc_leaf() which looks up the parent class, and is invoked prior to qdisc_create(), should return failure on not finding the class. In this patch, we leverage qdisc_leaf to return ERR_PTRs whenever the parentid doesn't correspond to a class, so that we can detect it earlier on and abort before qdisc_create is called. [1] https://lore.kernel.org/netdev/d912cbd7-193b-4269-9857-525bee8bbb6a@gmail.com/

References

Scores

VersionScoreVectorScored by
CVSS 3.1MEDIUM 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HNVD · nvd@nist.gov (Primary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 < 923a276c74e25073ae391e930792ac86a9f77f1e ; affected 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 < 90436e72c9622c2f70389070088325a3232d339f ; affected 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 < 25452638f133ac19d75af3f928327d8016952c8e ; affected 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 < 23c165dde88eac405eebb59051ea1fe139a45803 ; affected 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 < 4c691d1b6b6dbd73f30ed9ee7da05f037b0c49af ; affected 5e50da01d0ce7ef0ba3ed6cfabd62f327da0aca6 < 8ecd651ef24ab50123692a4e3e25db93cb11602a
Linux · Linuxaffected 2.6.20 ; unaffected 0 < 2.6.20 ; unaffected 5.4.296 ≤ 5.4.* ; unaffected 5.10.240 ≤ 5.10.* ; unaffected 5.15.189 ≤ 5.15.* ; unaffected 6.1.146 ≤ 6.1.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD