CVE-2025-21919

Description

In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix potential memory corruption in child_cfs_rq_on_list child_cfs_rq_on_list attempts to convert a 'prev' pointer to a cfs_rq. This 'prev' pointer can originate from struct rq's leaf_cfs_rq_list, making the conversion invalid and potentially leading to memory corruption. Depending on the relative positions of leaf_cfs_rq_list and the task group (tg) pointer within the struct, this can cause a memory fault or access garbage data. The issue arises in list_add_leaf_cfs_rq, where both cfs_rq->leaf_cfs_rq_list and rq->leaf_cfs_rq_list are added to the same leaf list. Also, rq->tmp_alone_branch can be set to rq->leaf_cfs_rq_list. This adds a check `if (prev == &rq->leaf_cfs_rq_list)` after the main conditional in child_cfs_rq_on_list. This ensures that the container_of operation will convert a correct cfs_rq struct. This check is sufficient because only cfs_rqs on the same CPU are added to the list, so verifying the 'prev' pointer against the current rq's list head is enough. Fixes a potential memory corruption issue that due to current struct layout might not be manifesting as a crash but could lead to unpredictable behavior when the layout changes.

Gravité et risque d'exploitation

CVE-2025-21919 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.23 %, ce qui la place devant 13.2 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, 6.6.83, <9cc7f0018609f75a349e42e3aebc3b0e905ba775, <=6.12.*, 6.1.131, <5.13, 0, 6.12.19, <3b4035ddbfc8e4521f85569998a7569668cccf51, 6.13.7, 6.14, <=6.6.*, 5.13, <5cb300dcdd27e6a351ac02541e0231261c775852, <e1dd09df30ba86716cb2ffab97dc35195c01eb8f, 5.15.179, <000c9ee43928f2ce68a156dd40bab7616256f4dd, fdaba61ef8a268d4136d0a113d153f7a89eb9984, <=*, <=5.15.*, <b5741e4b9ef3567613b2351384f91d3f16e59986, <=6.13.*) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/5cb300dcdd27e6a351ac02541e0231261c775852
• https://git.kernel.org/stable/c/000c9ee43928f2ce68a156dd40bab7616256f4dd
• https://git.kernel.org/stable/c/9cc7f0018609f75a349e42e3aebc3b0e905ba775
• https://git.kernel.org/stable/c/b5741e4b9ef3567613b2351384f91d3f16e59986
• https://git.kernel.org/stable/c/e1dd09df30ba86716cb2ffab97dc35195c01eb8f
• https://git.kernel.org/stable/c/3b4035ddbfc8e4521f85569998a7569668cccf51