# CVE-2022-49955: powerpc/rtas: Fix RTAS MSR[HV] handling for Cell

CVE-2022-49955 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-49955, released June 18, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-49955
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 18, 2025
- Weakness: NULL Pointer Dereference
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-49955

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.0.2-1 | [DEBIAN-CVE-2022-49955](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49955.md) | Jun 18, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.0.2-1 | [DEBIAN-CVE-2022-49955](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49955.md) | Jun 18, 2025 |
| Linux | linux Debian 14 | 6.0.2-1 | [DEBIAN-CVE-2022-49955](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49955.md) | Jun 18, 2025 |

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