CVE-2025-21919: sched/fair: Fix potential memory corruption in child_cfs_rq_on_list
First published: Tue Apr 01 2025(Updated: )
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.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | ||
| Linux Kernel | >=5.13<5.15.179 | |
| Linux Kernel | >=5.16<6.1.131 | |
| Linux Kernel | >=6.2<6.6.83 | |
| Linux Kernel | >=6.7<6.12.19 | |
| Linux Kernel | >=6.13<6.13.7 | |
| Linux Kernel | =6.14-rc1 | |
| Linux Kernel | =6.14-rc2 | |
| Linux Kernel | =6.14-rc3 | |
| Linux Kernel | =6.14-rc4 | |
| Linux Kernel | =6.14-rc5 |
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Reference Links
- 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
Frequently Asked Questions
What is the severity of CVE-2025-21919?
CVE-2025-21919 is classified as a high-severity vulnerability due to the potential for memory corruption.
How do I fix CVE-2025-21919?
To fix CVE-2025-21919, update your Linux kernel to the latest version where this vulnerability has been patched.
What impact does CVE-2025-21919 have on system security?
CVE-2025-21919 may allow an attacker to exploit memory corruption, leading to system instability or unauthorized access.
Which versions of the Linux kernel are affected by CVE-2025-21919?
CVE-2025-21919 affects various versions of the Linux kernel prior to the patch release.
Is CVE-2025-21919 related to scheduling issues in the Linux kernel?
Yes, CVE-2025-21919 is related to potential flaws in the scheduling mechanism of the Linux kernel.
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