CVE-2026-80633

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/cc69d0332421fd2943b66dbe5e597bf4fd5af126
• https://git.kernel.org/stable/c/e745cd2c749e557c14a15ac931761c3f58c24489

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