Look up another CVE · open CVE-2026-80633 in the interactive tracker
CVE-2026-80633
iommufd: Take dma_resv lock before dma_buf_unpin() in release path
Published 2026-08-28 (2 months ago) by the Linux kernel CNA. Subsystem drivers/iommu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-80633 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/iommu/iommufd/pages.c
- What this is
- IOMMUFDMAINTAINERS section matched on drivers/iommu/iommufd/ · iommu@lists.linux.dev · Maintained
Check it on the machine
grep -w CONFIG_IOMMUFD /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian does not build this code in 3 releases. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixie, forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_IOMMUFD
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-28 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/iommu
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 7.1 | 7.1.5 | cc69d0332421 |
| 7.1 | 7.2 | e745cd2c749e |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached only via local syscalls on /dev/iommu or VFIO-compat iommufd: open, IOMMU_IOAS_MAP_FILE with a dma-buf fd, then IOMMU_IOAS_UNMAP/close triggers iopt_release_pages()->dma_buf_unpin(); no network or packet handler is involved.
- AC:LAttack complexity, low
- Every teardown of the last dma-buf-backed iopt_pages deterministically hits dma_buf_unpin() without dma_resv; an attacker also controls concurrent invalidate/revoke via IOMMU_IOAS_UNMAP and dma_buf_invalidate_mappings (selftest revoke or VFIO PCI dmabuf revoke).
- PR:LPrivileges required, low
- No init-namespace root or special capability is required for the IOAS map/unmap path once a process can open iommufd (0660) and hold a compatible dma-buf fd, as in cloud GPU/VFIO passthrough tenants or iommufd selftests.
- UI:NUser interaction, none
- Exploitation requires no victim interaction; the attacker programmatically creates the IOAS dma-buf mapping and drives unmap/close and optional concurrent revoke through their own file descriptors and ioctl calls.
- S:CScope, changed
- Missing dma_resv locking during dma-buf unpin/detach races dma_buf_invalidate_mappings and can leave stale IOMMU IOVA-to-physical mappings or permit buffer movement while DMA views remain, breaking the IOMMU/DMA isolation boundary.
- C:HConfidentiality impact, high
- Concurrent dma_resv-protected invalidation during unpin without the reservation lock can race teardown of iopt_pages/dmabuf attachments and yield kernel heap use-after-free or stale mapping visibility exploitable for arbitrary kernel memory read.
- I:HIntegrity impact, high
- Racing unpin without dma_resv against invalidate/revoke can leave IOMMU page tables pointing at repinned/moved exporter pages, giving a device DMA write primitive to attacker-influenced physical memory and enabling control-flow corruption.
- A:HAvailability impact, high
- The missing lock triggers dma_resv_assert_held WARN on every dma-buf IOAS unmap/destroy (reproduced in iommufd selftests), and concurrent teardown races can provoke kernel oops/panic or wedge GPU/VFIO+iommufd workloads.