CVE-2024-47702

{"id": "CVE-2024-47702", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.8}]}, "published": "2024-10-21T12:15:06.743", "references": [{"url": "https://git.kernel.org/stable/c/92de36080c93296ef9005690705cba260b9bd68a", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/f09757fe97a225ae505886eac572e4cbfba96537", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/f1620c93a1ec950d87ef327a565d3907736d3340", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "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 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-&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 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 &gt; r0 goto pc+1 ... Tenga en cuenta que 'r2 = (s32)r2' puede hacer que la direcci\u00f3n __sk_buff-&gt;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-&gt;data; void *data_end = (void *)(long)skb-&gt;data_end; ... y generar\u00e1 r2 = *(u64 *)(r1 +208) r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 &gt; r0 goto pc+1 Si permitimos la extensi\u00f3n de signo, void *data = (void *)(long)(int)skb-&gt;data; void *data_end = (void *)(long)skb-&gt;data_end; ... el c\u00f3digo generado se ve as\u00ed 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 causar\u00e1 un error de verificaci\u00f3n ya que \"r2 &lt;&lt;= 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-&gt;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/"}], "lastModified": "2024-10-24T13:30:59.247", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "5E608BB9-C140-4A10-AE7A-FC5B5D4C1972", "versionEndExcluding": "6.10.13", "versionStartIncluding": "6.6"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "AB755D26-97F4-43B6-8604-CD076811E181", "versionEndExcluding": "6.11.2", "versionStartIncluding": "6.11"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}