---
id: CVE-2022-49955
title: 'powerpc/rtas: Fix RTAS MSR[HV] handling for Cell'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  powerpc/rtas: Fix RTAS MSR[HV] handling for Cell

  The semi-recent changes to MSR handling when entering RTAS (firmware)
  cause crashes on IBM Cell machines. An example t…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= b6b1c3ce06ca438eb24e0f45bf0e63ecad0369f5 <
    8b08d4f97233d8e58fff2fd9d5f86397a49733c5
  - >-
    Linux >= b6b1c3ce06ca438eb24e0f45bf0e63ecad0369f5 <
    91926d8b7e71aaf5f84f0cf208fc5a8b7a761050
  - Linux 5ca40fcf0da0ce2b5bc44e7d8b036535955f2e3d
  - Linux 5f4367448f6817c8a0e94dc9736ed84fa8eee4a3
  - Linux c9c41f0273826a13ac93124e66a4ff45df281ba0
  - Linux >= 5.15.46 < 5.16
  - Linux >= 5.17.14 < 5.18
  - Linux >= 5.18.3 < 5.19
  - Linux 5.19
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T19:51:57.598889Z'
published: '2025-06-18'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:00:12.210Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2022-49955'
references:
  - url: 'https://git.kernel.org/stable/c/8b08d4f97233d8e58fff2fd9d5f86397a49733c5'
  - url: 'https://git.kernel.org/stable/c/91926d8b7e71aaf5f84f0cf208fc5a8b7a761050'
tags:
  - cve.org
epss: 0.00209
epssPercentile: 0.11123
ingestedAt: '2026-11-05T22:38:31.629Z'
---

## Overview

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

powerpc/rtas: Fix RTAS MSR[HV] handling for Cell

The semi-recent changes to MSR handling when entering RTAS (firmware)
cause crashes on IBM Cell machines. An example trace:

  kernel tried to execute user page (2fff01a8) - exploit attempt? (uid: 0)
  BUG: Unable to handle kernel instruction fetch
  Faulting instruction address: 0x2fff01a8
  Oops: Kernel access of bad area, sig: 11 [#1]
  BE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=4 NUMA Cell
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W          6.0.0-rc2-00433-gede0a8d3307a #207
  NIP:  000000002fff01a8 LR: 0000000000032608 CTR: 0000000000000000
  REGS: c0000000015236b0 TRAP: 0400   Tainted: G        W           (6.0.0-rc2-00433-gede0a8d3307a)
  MSR:  0000000008001002 <ME,RI>  CR: 00000000  XER: 20000000
  ...
  NIP 0x2fff01a8
  LR  0x32608
  Call Trace:
    0xc00000000143c5f8 (unreliable)
    .rtas_call+0x224/0x320
    .rtas_get_boot_time+0x70/0x150
    .read_persistent_clock64+0x114/0x140
    .read_persistent_wall_and_boot_offset+0x24/0x80
    .timekeeping_init+0x40/0x29c
    .start_kernel+0x674/0x8f0
    start_here_common+0x1c/0x50

Unlike PAPR platforms where RTAS is only used in guests, on the IBM Cell
machines Linux runs with MSR[HV] set but also uses RTAS, provided by
SLOF.

Fix it by copying the MSR[HV] bit from the MSR value we've just read
using mfmsr into the value used for RTAS.

It seems like we could also fix it using an #ifdef CELL to set MSR[HV],
but that doesn't work because it's possible to build a single kernel
image that runs on both Cell native and pseries.

## Affected

- `Linux >= b6b1c3ce06ca438eb24e0f45bf0e63ecad0369f5 < 8b08d4f97233d8e58fff2fd9d5f86397a49733c5`
- `Linux >= b6b1c3ce06ca438eb24e0f45bf0e63ecad0369f5 < 91926d8b7e71aaf5f84f0cf208fc5a8b7a761050`
- `Linux 5ca40fcf0da0ce2b5bc44e7d8b036535955f2e3d`
- `Linux 5f4367448f6817c8a0e94dc9736ed84fa8eee4a3`
- `Linux c9c41f0273826a13ac93124e66a4ff45df281ba0`
- `Linux >= 5.15.46 < 5.16`
- `Linux >= 5.17.14 < 5.18`
- `Linux >= 5.18.3 < 5.19`
- `Linux 5.19`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.