CVE-2024-45020 bpf: Fix a kernel verifier crash in stacksafe()

2024-09-1115:13:54

Linux

www.cve.org

linux kernel

kernel verifier crash

bpf vulnerability

stacksafe

memory access

EPSS

Percentile

5.1%

JSON

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

bpf: Fix a kernel verifier crash in stacksafe()

Daniel Hodges reported a kernel verifier crash when playing with sched-ext.
Further investigation shows that the crash is due to invalid memory access
in stacksafe(). More specifically, it is the following code:

if (exact != NOT_EXACT &&
    old-&gt;stack[spi].slot_type[i % BPF_REG_SIZE] !=
    cur-&gt;stack[spi].slot_type[i % BPF_REG_SIZE])
        return false;

The ‘i’ iterates old->allocated_stack.
If cur->allocated_stack < old->allocated_stack the out-of-bound
access will happen.

To fix the issue add ‘i >= cur->allocated_stack’ check such that if
the condition is true, stacksafe() should fail. Otherwise,
cur->stack[spi].slot_type[i % BPF_REG_SIZE] memory access is legal.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/bpf/verifier.c"
    ],
    "versions": [
      {
        "version": "ab470fefce28",
        "lessThan": "7cad3174cc79",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "2793a8b015f7",
        "lessThan": "6e3987ac310c",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "2793a8b015f7",
        "lessThan": "bed2eb964c70",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "kernel/bpf/verifier.c"
    ],
    "versions": [
      {
        "version": "6.7",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.7",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.48",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.7",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]