fkie_cve-2024-47702
Vulnerability from fkie_nvd
Published
2024-10-21 12:15
Modified
2024-10-24 13:30
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fail verification for sign-extension of packet data/data_end/data_meta syzbot reported a kernel crash due to commit 1f1e864b6555 ("bpf: Handle sign-extenstin ctx member accesses"). The reason is due to sign-extension of 32-bit load for packet data/data_end/data_meta uapi field. The original code looks like: r2 = *(s32 *)(r1 + 76) /* load __sk_buff->data */ r3 = *(u32 *)(r1 + 80) /* load __sk_buff->data_end */ r0 = r2 r0 += 8 if r3 > r0 goto +1 ... Note that __sk_buff->data load has 32-bit sign extension. After verification and convert_ctx_accesses(), the final asm code looks like: r2 = *(u64 *)(r1 +208) r2 = (s32)r2 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 > r0 goto pc+1 ... Note that 'r2 = (s32)r2' may make the kernel __sk_buff->data address invalid which may cause runtime failure. Currently, in C code, typically we have void *data = (void *)(long)skb->data; void *data_end = (void *)(long)skb->data_end; ... and it will generate r2 = *(u64 *)(r1 +208) r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 > r0 goto pc+1 If we allow sign-extension, void *data = (void *)(long)(int)skb->data; void *data_end = (void *)(long)skb->data_end; ... the generated code looks like r2 = *(u64 *)(r1 +208) r2 <<= 32 r2 s>>= 32 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 > r0 goto pc+1 and this will cause verification failure since "r2 <<= 32" is not allowed as "r2" is a packet pointer. To fix this issue for case r2 = *(s32 *)(r1 + 76) /* load __sk_buff->data */ this patch added additional checking in is_valid_access() callback function for packet data/data_end/data_meta access. If those accesses are with sign-extenstion, the verification will fail. [1] https://lore.kernel.org/bpf/000000000000c90eee061d236d37@google.com/
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/92de36080c93296ef9005690705cba260b9bd68aPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f09757fe97a225ae505886eac572e4cbfba96537Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f1620c93a1ec950d87ef327a565d3907736d3340Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *


To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "5E608BB9-C140-4A10-AE7A-FC5B5D4C1972",
              "versionEndExcluding": "6.10.13",
              "versionStartIncluding": "6.6",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "AB755D26-97F4-43B6-8604-CD076811E181",
              "versionEndExcluding": "6.11.2",
              "versionStartIncluding": "6.11",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fail verification for sign-extension of packet data/data_end/data_meta\n\nsyzbot reported a kernel crash due to\n  commit 1f1e864b6555 (\"bpf: Handle sign-extenstin ctx member accesses\").\nThe reason is due to sign-extension of 32-bit load for\npacket data/data_end/data_meta uapi field.\n\nThe original code looks like:\n        r2 = *(s32 *)(r1 + 76) /* load __sk_buff-\u003edata */\n        r3 = *(u32 *)(r1 + 80) /* load __sk_buff-\u003edata_end */\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto +1\n        ...\nNote that __sk_buff-\u003edata load has 32-bit sign extension.\n\nAfter verification and convert_ctx_accesses(), the final asm code looks like:\n        r2 = *(u64 *)(r1 +208)\n        r2 = (s32)r2\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto pc+1\n        ...\nNote that \u0027r2 = (s32)r2\u0027 may make the kernel __sk_buff-\u003edata address invalid\nwhich may cause runtime failure.\n\nCurrently, in C code, typically we have\n        void *data = (void *)(long)skb-\u003edata;\n        void *data_end = (void *)(long)skb-\u003edata_end;\n        ...\nand it will generate\n        r2 = *(u64 *)(r1 +208)\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto pc+1\n\nIf we allow sign-extension,\n        void *data = (void *)(long)(int)skb-\u003edata;\n        void *data_end = (void *)(long)skb-\u003edata_end;\n        ...\nthe generated code looks like\n        r2 = *(u64 *)(r1 +208)\n        r2 \u003c\u003c= 32\n        r2 s\u003e\u003e= 32\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto pc+1\nand this will cause verification failure since \"r2 \u003c\u003c= 32\" is not allowed\nas \"r2\" is a packet pointer.\n\nTo fix this issue for case\n  r2 = *(s32 *)(r1 + 76) /* load __sk_buff-\u003edata */\nthis patch added additional checking in is_valid_access() callback\nfunction for packet data/data_end/data_meta access. If those accesses\nare with sign-extenstion, the verification will fail.\n\n  [1] https://lore.kernel.org/bpf/000000000000c90eee061d236d37@google.com/"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: bpf: Error en la verificaci\u00f3n de la extensi\u00f3n de signo del paquete data/data_end/data_meta syzbot inform\u00f3 de un fallo del kernel debido a el commit 1f1e864b6555 (\"bpf: Manejar los accesos a miembros ctx de la extensi\u00f3n de signo\"). La raz\u00f3n se debe a la extensi\u00f3n de signo de la carga de 32 bits para el campo uapi del paquete data/data_end/data_meta. El c\u00f3digo original se ve as\u00ed: r2 = *(s32 *)(r1 + 76) /* load __sk_buff-\u0026gt;data */ r3 = *(u32 *)(r1 + 80) /* load __sk_buff-\u0026gt;data_end */ r0 = r2 r0 += 8 if r3 \u0026gt; r0 goto +1 ... Tenga en cuenta que la carga de __sk_buff-\u0026gt;data tiene una extensi\u00f3n de signo de 32 bits. Despu\u00e9s de la verificaci\u00f3n y convert_ctx_accesses(), el c\u00f3digo asm final se ve as\u00ed: r2 = *(u64 *)(r1 +208) r2 = (s32)r2 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 \u0026gt; r0 goto pc+1 ... Tenga en cuenta que \u0027r2 = (s32)r2\u0027 puede hacer que la direcci\u00f3n __sk_buff-\u0026gt;data del n\u00facleo sea inv\u00e1lida, lo que puede causar un error en tiempo de ejecuci\u00f3n. Actualmente, en el c\u00f3digo C, normalmente tenemos void *data = (void *)(long)skb-\u0026gt;data; void *data_end = (void *)(long)skb-\u0026gt;data_end; ... y generar\u00e1 r2 = *(u64 *)(r1 +208) r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 \u0026gt; r0 goto pc+1 Si permitimos la extensi\u00f3n de signo, void *data = (void *)(long)(int)skb-\u0026gt;data; void *data_end = (void *)(long)skb-\u0026gt;data_end; ... el c\u00f3digo generado se ve as\u00ed r2 = *(u64 *)(r1 +208) r2 \u0026lt;\u0026lt;= 32 r2 s\u0026gt;\u0026gt;= 32 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 \u0026gt; r0 goto pc+1 y esto causar\u00e1 un error de verificaci\u00f3n ya que \"r2 \u0026lt;\u0026lt;= 32\" no est\u00e1 permitido ya que \"r2\" es un puntero de paquete. Para solucionar este problema en el caso r2 = *(s32 *)(r1 + 76) /* load __sk_buff-\u0026gt;data */, este parche agreg\u00f3 una verificaci\u00f3n adicional en la funci\u00f3n de devoluci\u00f3n de llamada is_valid_access() para el acceso a los paquetes data/data_end/data_meta. Si esos accesos son con la extensi\u00f3n sign-extenstion, la verificaci\u00f3n fallar\u00e1. [1] https://lore.kernel.org/bpf/000000000000c90eee061d236d37@google.com/"
    }
  ],
  "id": "CVE-2024-47702",
  "lastModified": "2024-10-24T13:30:59.247",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2024-10-21T12:15:06.743",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/92de36080c93296ef9005690705cba260b9bd68a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/f09757fe97a225ae505886eac572e4cbfba96537"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/f1620c93a1ec950d87ef327a565d3907736d3340"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}


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