CVE-2025-68292
Description
In the Linux kernel, the following vulnerability has been resolved:
mm/memfd: fix information leak in hugetlb folios
When allocating hugetlb folios for memfd, three initialization steps are missing:
- Folios are not zeroed, leading to kernel memory disclosure to userspace
- Folios are not marked uptodate before adding to page cache
- hugetlb_fault_mutex is not taken before hugetlb_add_to_page_cache()
The memfd allocation path bypasses the normal page fault handler (hugetlb_no_page) which would handle all of these initialization steps. This is problematic especially for udmabuf use cases where folios are pinned and directly accessed by userspace via DMA.
Fix by matching the initialization pattern used in hugetlb_no_page(): - Zero the folio using folio_zero_user() which is optimized for huge pages - Mark it uptodate with folio_mark_uptodate() - Take hugetlb_fault_mutex before adding to page cache to prevent races
The folio_zero_user() change also fixes a potential security issue where uninitialized kernel memory could be disclosed to userspace through read() or mmap() operations on the memfd.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A missing folio zeroing in Linux kernel's hugetlb memfd allocation leaks uninitialized kernel memory to userspace, fixed by aligning with proper initialization.
Vulnerability
Analysis
CVE-2025-68292 describes a security flaw in the Linux kernel's handling of hugetlb folios allocated for memfd. When allocating hugetlb folios are allocated for memfd, three critical initialization steps are missing: the folios are not zeroed, not zeroed, not marked uptodate before adding to page cache, and the hugetlb_fault_mutex is not taken before adding to the page cache. This bypasses the normal page fault handler (hugetlb_no_page) which would handle these steps [1].
Exploitation
The vulnerability is exploitable through memfd operations, particularly in udmabuf use cases where folios are pinned and directly accessed by userspace via DMA. An attacker with local access can trigger the allocation of hugetlb folios for memfd, which then contain uninitialized kernel memory. This memory can be disclosed to userspace through read() or mmap() operations on the memfd [1].
Impact
An attacker can read() or mmap() operations on the memfd can disclose uninitialized kernel memory to userspace, leading to an information leak. This could expose sensitive kernel data to an attacker with local access [1].
Mitigation
The fix is included in the Linux kernel stable commit 50b4c1c28733a536d. The patch ensures that hugetlb folios are zeroed using folio_zero_user(), marked uptodate with folio_mark_uptodate(), and the hugetlb_fault_mutex is taken before adding to page cache [1]. Users should apply the latest kernel updates to mitigate this vulnerability.
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
1Patches
0No patches discovered yet.
Vulnerability mechanics
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References
3News mentions
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