CVE-2026-80633

Received Received - Intake

Race Condition in Linux Kernel iommufd Component

Publication date: 2026-08-28

Last updated on: 2026-08-29

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: iommufd: Take dma_resv lock before dma_buf_unpin() in release path dma_buf_unpin() requires the caller to hold the exporter's dma_resv lock: void dma_buf_unpin(struct dma_buf_attachment *attach) { ... dma_resv_assert_held(dmabuf->resv); ... } iopt_release_pages() calls dma_buf_unpin() without taking that lock, so every iommufd_ioas_destroy()/iommufd_ioas_unmap() that releases the last reference on a DMABUF-backed iopt_pages triggers a WARN. This was hit while running tools/testing/selftests/iommu/iommufd: WARNING: drivers/dma-buf/dma-buf.c:1137 at dma_buf_unpin+0x62/0x70 RIP: 0010:dma_buf_unpin+0x62/0x70 Call Trace: <TASK> dma_buf_unpin+0x62/0x70 iopt_release_pages+0xe4/0x190 iopt_unmap_iova_range+0x1c7/0x290 iopt_unmap_all+0x1a/0x30 iommufd_ioas_destroy+0x1d/0x50 iommufd_fops_release+0x93/0x150 __fput+0xfc/0x2c0 __x64_sys_close+0x3d/0x80 do_syscall_64+0x65/0x180 </TASK> Take the dma_resv lock around dma_buf_unpin() in iopt_release_pages(), matching the iopt_map_dmabuf() convention. dma_buf_detach() acquires the reservation lock internally, so it must remain outside the locked region.

CVSS Scores

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Meta Information

Published

2026-08-28

Last Modified

2026-08-29

Generated

2026-09-17

AI Q&A

2026-08-28

EPSS Evaluated

2026-09-15

NVD

CVE-2026-80633

EUVD

EUVD-2026-67509

Affected Vendors & Products

Vendor	Product	Version / Range
linux_kernel	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a missing dma_resv lock in the iommufd release path. Specifically, the function iopt_release_pages() calls dma_buf_unpin() without holding the required dma_resv lock, which can trigger a kernel warning. The issue occurs during the destruction of DMABUF-backed iopt_pages in operations like iommufd_ioas_destroy() or iommufd_ioas_unmap().

Detection Guidance

This vulnerability is specific to the Linux kernel's iommufd subsystem and may trigger a kernel warning when releasing DMABUF-backed memory. Detection involves monitoring kernel logs for WARN messages related to dma_buf_unpin or iopt_release_pages during operations like iommufd_ioas_destroy or iommufd_ioas_unmap.

Impact Analysis

This vulnerability may cause kernel warnings or errors during system operations involving DMABUF-backed memory in iommufd. While it does not directly compromise security, repeated warnings could indicate instability or potential for further issues in memory management subsystems.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it is a Linux kernel memory management issue related to DMA buffer handling. Compliance impacts would depend on specific system configurations and usage, not the vulnerability itself.

Mitigation Strategies

Apply the Linux kernel patch that resolves this issue by ensuring the dma_resv lock is held before calling dma_buf_unpin in iopt_release_pages. Update to a kernel version containing the fix or backport the patch to your current kernel.

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