CVE-2025-38434

{"id": "CVE-2025-38434", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "[email protected]", "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": "2025-07-25T15:15:28.707", "references": [{"url": "https://git.kernel.org/stable/c/890ba5be6335dbbbc99af14ea007befb5f83f174", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/f8b1898748dfeb4f9b67b6a6d661f354b9de3523", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/fe30c30bf3bb68d4a4d8c7c814769857b5c973e6", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "[email protected]", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"riscv: Define TASK_SIZE_MAX for __access_ok()\"\n\nThis reverts commit ad5643cf2f69 (\"riscv: Define TASK_SIZE_MAX for\n__access_ok()\").\n\nThis commit changes TASK_SIZE_MAX to be LONG_MAX to optimize access_ok(),\nbecause the previous TASK_SIZE_MAX (default to TASK_SIZE) requires some\ncomputation.\n\nThe reasoning was that all user addresses are less than LONG_MAX, and all\nkernel addresses are greater than LONG_MAX. Therefore access_ok() can\nfilter kernel addresses.\n\nAddresses between TASK_SIZE and LONG_MAX are not valid user addresses, but\naccess_ok() let them pass. That was thought to be okay, because they are\nnot valid addresses at hardware level.\n\nUnfortunately, one case is missed: get_user_pages_fast() happily accepts\naddresses between TASK_SIZE and LONG_MAX. futex(), for instance, uses\nget_user_pages_fast(). This causes the problem reported by Robert [1].\n\nTherefore, revert this commit. TASK_SIZE_MAX is changed to the default:\nTASK_SIZE.\n\nThis unfortunately reduces performance, because TASK_SIZE is more expensive\nto compute compared to LONG_MAX. But correctness first, we can think about\noptimization later, if required."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: Revertir \"riscv: Define TASK_SIZE_MAX for __access_ok()\". Esto revierte el commit ad5643cf2f69 (\"riscv: Define TASK_SIZE_MAX for __access_ok()\"). Este commit cambia TASK_SIZE_MAX a LONG_MAX para optimizar access_ok(), ya que el valor predeterminado de TASK_SIZE_MAX (predeterminado) requiere c\u00e1lculos. El razonamiento era que todas las direcciones de usuario son menores que LONG_MAX y todas las direcciones de kernel son mayores que LONG_MAX. Por lo tanto, access_ok() puede filtrar direcciones de kernel. Las direcciones entre TASK_SIZE y LONG_MAX no son direcciones de usuario v\u00e1lidas, pero access_ok() las deja pasar. Se consider\u00f3 que esto era correcto, ya que no son direcciones v\u00e1lidas a nivel de hardware. Desafortunadamente, se omite un caso: get_user_pages_fast() acepta direcciones entre TASK_SIZE y LONG_MAX. futex(), por ejemplo, usa get_user_pages_fast(). Esto causa el problema reportado por Robert [1]. Por lo tanto, revierte este commit . TASK_SIZE_MAX se cambia al valor predeterminado: TASK_SIZE. Lamentablemente, esto reduce el rendimiento, ya que TASK_SIZE es m\u00e1s costoso de calcular que LONG_MAX. Pero primero la correcci\u00f3n; podemos pensar en la optimizaci\u00f3n m\u00e1s adelante, si es necesario."}], "lastModified": "2025-11-19T18:08:53.590", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "7D12ED65-B7F2-463D-B728-1F34443EA43B", "versionEndExcluding": "6.12.36", "versionStartIncluding": "6.10"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "0CC768E2-3BBC-4A6E-9C2F-ECB27A703C2D", "versionEndExcluding": "6.15.5", "versionStartIncluding": "6.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.16:rc1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "6D4894DB-CCFE-4602-B1BF-3960B2E19A01"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.16:rc2:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "09709862-E348-4378-8632-5A7813EDDC86"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.16:rc3:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "415BF58A-8197-43F5-B3D7-D1D63057A26E"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}