CVE-2024-27022: fork: defer linking file vma until vma is fully initialized

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-01 · updated 2026-10-30
Weakness: CWE-908

Description

In the Linux kernel, the following vulnerability has been resolved: fork: defer linking file vma until vma is fully initialized Thorvald reported a WARNING [1]. And the root cause is below race: CPU 1 CPU 2 fork hugetlbfs_fallocate dup_mmap hugetlbfs_punch_hole i_mmap_lock_write(mapping); vma_interval_tree_insert_after -- Child vma is visible through i_mmap tree. i_mmap_unlock_write(mapping); hugetlb_dup_vma_private -- Clear vma_lock outside i_mmap_rwsem! i_mmap_lock_write(mapping); hugetlb_vmdelete_list vma_interval_tree_foreach hugetlb_vma_trylock_write -- Vma_lock is cleared. tmp->vm_ops->open -- Alloc new vma_lock outside i_mmap_rwsem! hugetlb_vma_unlock_write -- Vma_lock is assigned!!! i_mmap_unlock_write(mapping); hugetlb_dup_vma_private() and hugetlb_vm_op_open() are called outside i_mmap_rwsem lock while vma lock can be used in the same time. Fix this by deferring linking file vma until vma is fully initialized. Those vmas should be initialized first before they can be used.

Affected products

Linux kernel: from 6.1 before 6.1.90; from 6.2 before 6.6.30; from 6.7 before 6.8.8; 6.9-rc1, 6.9-rc2, 6.9-rc3, 6.9-rc4 — fixed in 6.1.90, 6.6.30, 6.8.8
Linux: 6.1 — fixed in 6.9

How to fix

Upgrade to a fixed version: Linux kernel 6.1.90, 6.6.30, 6.8.8; Linux 6.9. Check the vendor advisory for mitigations.

References

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