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CVE-2026-90427
iommu/tegra241-cmdqv: Don't fall back to a freed smmu after devm_krealloc()
Published 2026-09-17 (31 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-2026-90427 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 | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| 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_cmdqv_probe() uses devm_krealloc() to grow @smmu into the larger tegra241_cmdqv, which frees the original @smmu once it relocates. A failure after that returned NULL, and the caller then dereferenced the freed @smmu on its fallback path. Return an int and take @smmu by reference instead, then update *smmu to the reallocated pointer after devm_krealloc() succeeds, so the caller and its fallback path both use the live @smmu rather than the freed original.
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
- 2026-09-17 (31 days ago)source
- CVSS
- 7.4 high
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.1% 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 |
|---|---|---|
| 6.12 | 6.18.57 | 268cbe3a36ae |
| 6.12 | 7.2.6 | 86197679b293 |
| 6.12 | 7.3 | d4d05f55e9da |
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 UAF is reached from arm_smmu_device_probe() → arm_smmu_impl_probe() → tegra241_cmdqv_probe() → __tegra241_cmdqv_probe() when ACPI IORT (acpi_iort_init()/iort_add_platform_device("arm-smmu-v3")) or DT nvidia,tegra264-smmu binds the SMMU. No protocol message supplies the stale pointer; it is a local devm_krealloc() lifetime bug.
- AC:HAttack complexity, high
- out_fallback uses the freed @smmu only if a relocating devm_krealloc() is followed by kzalloc_objs(cmdqv->vintfs) or request_threaded_irq() failing. arm_smmu_driver sets suppress_bind_attrs, CONFIG_ARM_SMMU_V3=y, and this probe never returns -EPROBE_DEFER, so a local attacker cannot re-enter it or reliably force those GFP_KERNEL/IRQ failures.
- PR:NPrivileges required, none
- arm_smmu_device_probe() has no capable() check; tegra241_cmdqv_probe() runs from the platform .probe in kernel_init once IORT creates the arm-smmu-v3 device or DT matches nvidia,tegra264-smmu. No OS account or user-namespace capability is required to be on that path.
- UI:NUser interaction, none
- tegra241_cmdqv_probe()’s out_fallback dereference of the freed @smmu runs inside arm_smmu_device_probe() during automatic platform bind; no victim must mount a filesystem, open a device node, or load a module by hand.
- S:UScope, unchanged
- The use-after-free is of the host kernel arm_smmu_device that devm_krealloc() freed in __tegra241_cmdqv_probe(); out_fallback’s smmu->options write and the rest of arm_smmu_device_probe() stay in that kernel. This is not leftover SMMU translation tables or a guest/DMA walk of attacker-controlled IOMMU page tables.
- C:HConfidentiality impact, high
- After a relocating devm_krealloc(), tegra241_cmdqv_probe() returns ERR_PTR(-ENODEV) and arm_smmu_impl_probe() hands the freed @smmu back to arm_smmu_device_probe(). That use-after-free of the SMMU object can be reclaimed and, per kernel UAF guidance, enables arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- out_fallback writes smmu->options through the freed pointer, then arm_smmu_device_probe() continues with arm_smmu_device_hw_probe(), arm_smmu_init_structures(), and iommu_device_register() on the same dangling arm_smmu_device, a write-after-free that yields heap-spray write and control-flow hijack primitives.
- A:HAvailability impact, high
- out_fallback dereferences smmu->impl_dev and later SMMU probe/runtime uses the freed arm_smmu_device; that use-after-free oopses or panics the kernel even when not turned into a full exploit.