---
id: "CVE-2026-98640"
kind: "vulnerability"
aliases: ["CVE-2026-98640"]
title: "Linux kernel: AMD sensor hub driver crashes on undersized PCI BAR"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["amd", "hid", "kernel", "laptops", "linux", "runtime"]
not_affected_if: ["driver-not-loaded", "no-amd-sfh-device"]
published_at: "2026-10-18T16:17:17+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:20:56+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98640", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: AMD sensor hub driver crashes on undersized PCI BAR

The amd_sfh HID driver maps PCI BAR 2 without checking its size, so a device exposing a smaller BAR causes an out-of-bounds MMIO read and a kernel page fault during probe. The sources describe a kernel oops (denial of service) and do not describe code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `uname -r` and compare against the fixed kernel version in the upstream commit, which the sources do not name.
- Run `lspci -v` and look for an AMD sensor fusion hub (MP2) device; check whether its BAR 2 region is smaller than 128KB.

## Fix

- Update to a Linux kernel build that includes the upstream commit 'HID: amd_sfh: Validate PCI BAR size before mapping'; the fixed version is unknown from the sources.

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98640

## From the sources

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

HID: amd_sfh: Validate PCI BAR size before mapping

The amd_sfh driver maps PCI BAR 2 using pcim_iomap_regions() and
subsequently accesses MMIO registers at offsets up to 0x10958 (e.g.,
AMD_P2C_MSG3 at 0x1068C). However, the driver never validates that the BAR
size is large enough to cover these accesses. If the driver is bound to a
device with a smaller BAR 2, this leads to an out-of-bounds memory access
and a page fault during the probe function.

For example, a page fault can occur when reading from privdata->mmio +
AMD_P2C_MSG3 in mp2_select_ops():

  BUG: unable to handle page fault for address: ffffc9000390368c
  PGD 100000067 P4D 100000067 PUD 1012c1067 PMD 105b64067 PTE 0
  Oops: Oops: 0000 [#1] SMP KASAN NOPTI
  RIP: 0010:readl arch/x86/include/asm/io.h:59 [inline]
  RIP: 0010:mp2_select_ops drivers/hid/amd-sfh-hid/amd_sfh_pcie.c:282
  [inline]
  RIP: 0010:amd_mp2_pci_probe+0x337/0x5f0
  drivers/hid/amd-sfh-hid/amd_sfh_pcie.c:487
  Call Trace:
   <TASK>
   local_pci_probe drivers/pci/pci-driver.c:332 [inline]
   pci_call_probe drivers/pci/pci-driver.c:394 [inline]
   __pci_device_probe drivers/pci/pci-driver.c:455 [inline]
   pci_device_probe+0x431/0xc90 drivers/pci/pci-driver.c:489

Fix this by verifying that the length of BAR 2 is at least 128KB before
attempting to map it. Since the maximum accessed offset is 0x10958, and PCI
BAR sizes are powers of 2, any legitimate hardware will have a BAR size of
at least 128KB.

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