CVE-2026-80633 iommufd: Take dma_resv lock before dma_buf_unpin() in release path
A missing lock in the Linux kernel iommufd release path causes a warning and potential instability when releasing DMABUF-backed pages.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80633?
CVE-2026-80633 is a high-severity vulnerability in Linux, published on 28 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-80633?
How do I fix CVE-2026-80633?
Apply the vendor's patch.
Is CVE-2026-80633 being exploited?
There is no known exploitation of CVE-2026-80633 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-80633, GHSA-xcxf-f2jh-rfhm, UBUNTU-CVE-2026-80633.