Release Date: | 2025-07-25 | |
Impact: | Moderate | What is this? |
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/
See more information about CVE-2025-38457 from MITRE CVE dictionary and NIST NVD
NOTE: The following CVSS metrics and score provided are preliminary and subject to review.
Base Score: | 7.0 |
Vector String: | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H |
Version: | 3.1 |
Attack Vector: | Local |
Attack Complexity: | High |
Privileges Required: | Low |
User Interaction: | None |
Scope: | Unchanged |
Confidentiality Impact: | High |
Integrity Impact: | High |
Availability Impact: | High |
Platform | Errata | Release Date |
Oracle Linux version 10 (kernel-uek) | ELSA-2025-20551 | 2025-09-08 |
Oracle Linux version 9 (kernel-uek) | ELSA-2025-20551 | 2025-09-08 |
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