CVE-2026-89450: iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field

CVE-2026-89450: iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field

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.

The Linux kernel CVE team has assigned CVE-2026-89450 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.17 with commit 4dc0d12474f9d4833c3dd96b73d61e406d3f5dc7 and fixed in 6.18.50 with commit d903d99ffd22b0180bd745a43f221c21bcdd8d7c
	Issue introduced in 6.17 with commit 4dc0d12474f9d4833c3dd96b73d61e406d3f5dc7 and fixed in 7.2.4 with commit 445204550f894ca325ac80a21e3df177ad073798
	Issue introduced in 6.17 with commit 4dc0d12474f9d4833c3dd96b73d61e406d3f5dc7 and fixed in 7.3-rc1 with commit 4379610c79bd88ddbea10e7f6c21e16d4b338c6b

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-89450
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/d903d99ffd22b0180bd745a43f221c21bcdd8d7c
	https://git.kernel.org/stable/c/445204550f894ca325ac80a21e3df177ad073798
	https://git.kernel.org/stable/c/4379610c79bd88ddbea10e7f6c21e16d4b338c6b