---
id: CVE-2023-53487
title: 'powerpc/rtas_flash: allow user copy to flash block cache objects'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  powerpc/rtas_flash: allow user copy to flash block cache objects

  With hardened usercopy enabled (CONFIG_HARDENED_USERCOPY=y), using the
  /proc/powerpc/rtas/firmware_upd…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    8f09cc15dcd91d16562400c51d24c7be0d5796fa
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    1d29e21ed09fa668416fa7721e08d451b9903485
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    0ba7f969be599e21d4b1f1e947593de6515f4996
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    8ef25fb13494e35c6dbe15445c7875fa92bc3e8b
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    b8fee83aa4ed3846c7f50a0b364bc699f48d96e5
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    6acb8a453388374fafb3c3b37534b675b2aa0ae1
  - >-
    Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 <
    4f3175979e62de3b929bfa54a0db4b87d36257a7
  - Linux 4.16
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:22:14.298181Z'
published: '2025-10-01'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:31:11.542Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2023-53487'
references:
  - url: 'https://git.kernel.org/stable/c/8f09cc15dcd91d16562400c51d24c7be0d5796fa'
  - url: 'https://git.kernel.org/stable/c/1d29e21ed09fa668416fa7721e08d451b9903485'
  - url: 'https://git.kernel.org/stable/c/0ba7f969be599e21d4b1f1e947593de6515f4996'
  - url: 'https://git.kernel.org/stable/c/8ef25fb13494e35c6dbe15445c7875fa92bc3e8b'
  - url: 'https://git.kernel.org/stable/c/b8fee83aa4ed3846c7f50a0b364bc699f48d96e5'
  - url: 'https://git.kernel.org/stable/c/6acb8a453388374fafb3c3b37534b675b2aa0ae1'
  - url: 'https://git.kernel.org/stable/c/4f3175979e62de3b929bfa54a0db4b87d36257a7'
tags:
  - cve.org
epss: 0.00168
epssPercentile: 0.06189
ingestedAt: '2026-11-05T22:38:31.802Z'
---

## Overview

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

powerpc/rtas_flash: allow user copy to flash block cache objects

With hardened usercopy enabled (CONFIG_HARDENED_USERCOPY=y), using the
/proc/powerpc/rtas/firmware_update interface to prepare a system
firmware update yields a BUG():

  kernel BUG at mm/usercopy.c:102!
  Oops: Exception in kernel mode, sig: 5 [#1]
  LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
  Modules linked in:
  CPU: 0 PID: 2232 Comm: dd Not tainted 6.5.0-rc3+ #2
  Hardware name: IBM,8408-E8E POWER8E (raw) 0x4b0201 0xf000004 of:IBM,FW860.50 (SV860_146) hv:phyp pSeries
  NIP:  c0000000005991d0 LR: c0000000005991cc CTR: 0000000000000000
  REGS: c0000000148c76a0 TRAP: 0700   Not tainted  (6.5.0-rc3+)
  MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 24002242  XER: 0000000c
  CFAR: c0000000001fbd34 IRQMASK: 0
  [ ... GPRs omitted ... ]
  NIP usercopy_abort+0xa0/0xb0
  LR  usercopy_abort+0x9c/0xb0
  Call Trace:
    usercopy_abort+0x9c/0xb0 (unreliable)
    __check_heap_object+0x1b4/0x1d0
    __check_object_size+0x2d0/0x380
    rtas_flash_write+0xe4/0x250
    proc_reg_write+0xfc/0x160
    vfs_write+0xfc/0x4e0
    ksys_write+0x90/0x160
    system_call_exception+0x178/0x320
    system_call_common+0x160/0x2c4

The blocks of the firmware image are copied directly from user memory
to objects allocated from flash_block_cache, so flash_block_cache must
be created using kmem_cache_create_usercopy() to mark it safe for user
access.

[mpe: Trim and indent oops]

## Affected

- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < 8f09cc15dcd91d16562400c51d24c7be0d5796fa`
- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < 1d29e21ed09fa668416fa7721e08d451b9903485`
- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < 0ba7f969be599e21d4b1f1e947593de6515f4996`
- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < 8ef25fb13494e35c6dbe15445c7875fa92bc3e8b`
- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < b8fee83aa4ed3846c7f50a0b364bc699f48d96e5`
- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < 6acb8a453388374fafb3c3b37534b675b2aa0ae1`
- `Linux >= 6d07d1cd300f4c7e16005f881fea388164999cc8 < 4f3175979e62de3b929bfa54a0db4b87d36257a7`
- `Linux 4.16`

## Remediation

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