CVE-2024-36943: fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan

Severity: medium (CVSS 4.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-30 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan make_uffd_wp_pte() was previously doing: pte = ptep_get(ptep); ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte); But if another thread accessed or dirtied the pte between the first 2 calls, this could lead to loss of that information. Since ptep_modify_prot_start() gets and clears atomically, the following is the correct pattern and prevents any possible race. Any access after the first call would see an invalid pte and cause a fault: pte = ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte);

Affected products

Linux kernel: from 6.7 before 6.8.10; 6.9-rc1, 6.9-rc2, 6.9-rc3, 6.9-rc4, 6.9-rc5, 6.9-rc6 (+1) — fixed in 6.8.10

How to fix

Upgrade to a fixed version: Linux kernel 6.8.10. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2024-36943 or the next vulnerability affects your stack