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CVE-2026-89450
iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/iommu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89450 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 | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
tegra241_vintf_init_vsid() programs the guest-provided vSID into SID_MATCH, whose VIRT_SID field spans bits [20:1] with bit 0 as the match-enable flag. The HW therefore matches only a 20-bit Stream ID. The bound check rejects only virt_sid > UINT_MAX, which admits a value far wider than the field. The write "virt_sid << 1 | 0x1" then drops every bit above 20: a virt_sid of 0x80000000 lands as SID_MATCH = 0x1, a valid match on vSID 0, so the entry aliases the wrong Stream ID. Because vdev->virt_id is guest-controlled, a VMM can trigger it. Validate virt_sid against the field width with FIELD_MAX(), and program the register with FIELD_PREP() so the value and the field stay consistent.
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/arm/arm-smmu-v3/tegra241-cmdqv.c
- What this is
- TEGRA IOMMU DRIVERSMAINTAINERS section matched on drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c · linux-tegra@vger.kernel.org · Supported
Check it on the machine
grep -wE 'CONFIG_ARM_SMMU_V3|CONFIG_TEGRA241_CMDQV' /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 switches
- CONFIG_ARM_SMMU_V3, CONFIG_TEGRA241_CMDQV
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-09-11 (37 days 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
- 0.13%, higher than 2.1% 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 |
|---|---|---|
| 6.17 | 6.18.50 | d903d99ffd22 |
| 6.17 | 7.2.4 | 445204550f89 |
| 6.17 | 7.3 | 4379610c79bd |
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
- Reached only via local ioctl on /dev/iommu or VFIO-compat /dev/vfio/vfio: iommufd_fops_ioctl() dispatches IOMMU_VDEVICE_ALLOC to iommufd_vdevice_alloc_ioctl(), which calls tegra241_vintf_init_vsid() to program SID_MATCH. There is no network or packet path into CMDQV SID programming.
- AC:LAttack complexity, low
- The attacker fully chooses cmd->virt_id; the old UINT_MAX check accepts values such as 0x80000000, and writel(virt_sid<<1|0x1) deterministically truncates them onto a 20-bit SID_MATCH (aliasing vSID 0). No race or uninfluenced memory layout is required on NVIDIA Grace/CMDQV.
- PR:LPrivileges required, low
- iommufd_fops_open() and the ioctl table have no capable() gate (/dev/iommu 0660, /dev/vfio/vfio 0666). A tenant or unprivileged QEMU user granted VFIO/iommufd access on Grace can bind a CMDQV-backed device, alloc a TEGRA241_CMDQV vIOMMU, and issue VDEVICE_ALLOC without init-namespace root.
- UI:NUser interaction, none
- The attacker performs the full sequence themselves (open iommufd, bind the assigned device, alloc vIOMMU/vDEVICE with a truncated virt_id, then guest ATC_INV via VCMDQ). No separate victim action such as mounting a filesystem is required.
- S:CScope, changed
- Truncating a guest-controlled vSID into SID_MATCH aliases it onto another Stream ID so CMDQV rewrites ATC_INV/CFGI to the wrong pSID. That is an IOMMU/DMA boundary bypass: missed invalidations leave stale ATS/IOTLB entries and let device DMA reach host memory outside the guest domain.
- C:HConfidentiality impact, high
- Wrong SID_MATCH/SID_REPLACE pairing leaves stale ATS translations after IOVA unmap, so a guest-controlled passthrough device can DMA-read host pages recycled by the allocator, yielding an arbitrary host-memory disclosure primitive through the IOMMU.
- I:HIntegrity impact, high
- The same stale or retargeted translations allow DMA writes into unmapped host pages, and aliased CFGI/ATC_INV operate on the wrong physical Stream ID, corrupting IOMMU translation state and providing an arbitrary write suitable for control-flow hijack.
- A:HAvailability impact, high
- Misdirected invalidation and CFGI cause SMMU translation faults, DMA into recycled kernel pages, and CMDQV GERROR/ISR failures that oops or panic the host; the truncated vSID can be programmed repeatedly on every VDEVICE_ALLOC.