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->data */\n        r3 = *(u32 *)(r1 + 80) /* load __sk_buff->data_end */\n        r0 = r2\n        r0 += 8\n        if r3 > r0 goto +1\n        ...\nNote that __sk_buff->data 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 > r0 goto pc+1\n        ...\nNote that 'r2 = (s32)r2' may make the kernel __sk_buff->data address invalid\nwhich may cause runtime failure.\n\nCurrently, in C code, typically we have\n        void *data = (void *)(long)skb->data;\n        void *data_end = (void *)(long)skb->data_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 > r0 goto pc+1\n\nIf we allow sign-extension,\n        void *data = (void *)(long)(int)skb->data;\n        void *data_end = (void *)(long)skb->data_end;\n        ...\nthe generated code looks like\n        r2 = *(u64 *)(r1 +208)\n        r2 <<= 32\n        r2 s>>= 32\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 > r0 goto pc+1\nand this will cause verification failure since \"r2 <<= 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->data */\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 verificación de la extensión de signo del paquete data/data_end/data_meta syzbot informó de un fallo del kernel debido a el commit 1f1e864b6555 (\"bpf: Manejar los accesos a miembros ctx de la extensión de signo\"). La razón se debe a la extensión de signo de la carga de 32 bits para el campo uapi del paquete data/data_end/data_meta. El código original se ve así: r2 = *(s32 *)(r1 + 76) /* load __sk_buff-&gt;data */ r3 = *(u32 *)(r1 + 80) /* load __sk_buff-&gt;data_end */ r0 = r2 r0 += 8 if r3 &gt; r0 goto +1 ... Tenga en cuenta que la carga de __sk_buff-&gt;data tiene una extensión de signo de 32 bits. Después de la verificación y convert_ctx_accesses(), el código asm final se ve así: r2 = *(u64 *)(r1 +208) r2 = (s32)r2 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 &gt; r0 goto pc+1 ... Tenga en cuenta que 'r2 = (s32)r2' puede hacer que la dirección __sk_buff-&gt;data del núcleo sea inválida, lo que puede causar un error en tiempo de ejecución. Actualmente, en el código C, normalmente tenemos void *data = (void *)(long)skb-&gt;data; void *data_end = (void *)(long)skb-&gt;data_end; ... y generará r2 = *(u64 *)(r1 +208) r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 &gt; r0 goto pc+1 Si permitimos la extensión de signo, void *data = (void *)(long)(int)skb-&gt;data; void *data_end = (void *)(long)skb-&gt;data_end; ... el código generado se ve así r2 = *(u64 *)(r1 +208) r2 &lt;&lt;= 32 r2 s&gt;&gt;= 32 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 &gt; r0 goto pc+1 y esto causará un error de verificación ya que \"r2 &lt;&lt;= 32\" no está permitido ya que \"r2\" es un puntero de paquete. Para solucionar este problema en el caso r2 = *(s32 *)(r1 + 76) /* load __sk_buff-&gt;data */, este parche agregó una verificación adicional en la función de devolución de llamada is_valid_access() para el acceso a los paquetes data/data_end/data_meta. Si esos accesos son con la extensión sign-extenstion, la verificación fallará. [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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