CVE-2025-38434

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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."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - The bug is reached only through local syscalls (futex(), read()/write() with user iovecs, io_uring fixed-buffer registration) in which the attacker supplies a crafted userspace virtual address; there is no network path to the vulnerable get_user_pages_fast() check.\nAC:L - Exploitation is fully deterministic \u2014 the attacker simply passes an address in [TASK_SIZE, LONG_MAX] to a gup_fast user; there is no race and no attacker-uncontrolled condition on an affected RISC-V 64-bit kernel.\nPR:L - Any unprivileged local user can invoke the affected syscalls (futex, read/write, io_uring); no capabilities or elevated privileges are required.\nUI:N - The attacker triggers the flaw entirely through their own syscalls with no action required from any other user.\nS:U - The vulnerability and its impact are both contained within the OS kernel's security authority; this is a standard in-kernel memory-safety boundary bug, not a VM/sandbox escape.\nC:H - The flaw lets an unprivileged user pin present kernel PTEs (the generic pte_access_permitted() does not check _PAGE_USER) and read arbitrary kernel memory out via write()-style transfers, a full kernel-memory disclosure primitive.\nI:H - Using FOLL_WRITE paths (e.g. read() into the crafted buffer) the same walk pins writable kernel pages, allowing attacker-controlled data to be written into kernel memory \u2014 an arbitrary kernel write enabling privilege escalation.\nA:H - Walking into the kernel half of the page tables and corrupting or dereferencing kernel structures can trivially oops/panic the kernel."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/riscv/include/asm/pgtable.h"], "versions": [{"version": "ad5643cf2f699989daa85d909403febd6712fccb", "lessThan": "fe30c30bf3bb68d4a4d8c7c814769857b5c973e6", "status": "affected", "versionType": "git"}, {"version": "ad5643cf2f699989daa85d909403febd6712fccb", "lessThan": "f8b1898748dfeb4f9b67b6a6d661f354b9de3523", "status": "affected", "versionType": "git"}, {"version": "ad5643cf2f699989daa85d909403febd6712fccb", "lessThan": "890ba5be6335dbbbc99af14ea007befb5f83f174", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/riscv/include/asm/pgtable.h"], "versions": [{"version": "6.10", "status": "affected"}, {"version": "0", "lessThan": "6.10", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.36", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.15.5", "lessThanOrEqual": "6.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.12.36"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.15.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.10", "versionEndExcluding": "6.16"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/fe30c30bf3bb68d4a4d8c7c814769857b5c973e6"}, {"url": "https://git.kernel.org/stable/c/f8b1898748dfeb4f9b67b6a6d661f354b9de3523"}, {"url": "https://git.kernel.org/stable/c/890ba5be6335dbbbc99af14ea007befb5f83f174"}], "title": "Revert \"riscv: Define TASK_SIZE_MAX for __access_ok()\"", "x_generator": {"engine": "bippy-1.2.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["arch/riscv/include/asm/pgtable.h"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "fe30c30bf3bb68d4a4d8c7c814769857b5c973e6", "status": "affected", "version": "ad5643cf2f699989daa85d909403febd6712fccb", "versionType": "git"}, {"lessThan": "f8b1898748dfeb4f9b67b6a6d661f354b9de3523", "status": "affected", "version": "ad5643cf2f699989daa85d909403febd6712fccb", "versionType": "git"}, {"lessThan": "890ba5be6335dbbbc99af14ea007befb5f83f174", "status": "affected", "version": "ad5643cf2f699989daa85d909403febd6712fccb", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["arch/riscv/include/asm/pgtable.h"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.10"}, {"lessThan": "6.10", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.36", "versionType": "semver"}, {"lessThanOrEqual": "6.15.*", "status": "unaffected", "version": "6.15.5", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "6.16", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "7D12ED65-B7F2-463D-B728-1F34443EA43B", "versionEndExcluding": "6.12.36", "versionStartIncluding": "6.10", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "0CC768E2-3BBC-4A6E-9C2F-ECB27A703C2D", "versionEndExcluding": "6.15.5", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.16:rc1:*:*:*:*:*:*", "matchCriteriaId": "6D4894DB-CCFE-4602-B1BF-3960B2E19A01", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.16:rc2:*:*:*:*:*:*", "matchCriteriaId": "09709862-E348-4378-8632-5A7813EDDC86", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.16:rc3:*:*:*:*:*:*", "matchCriteriaId": "415BF58A-8197-43F5-B3D7-D1D63057A26E", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "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."}], "id": "CVE-2025-38434", "lastModified": "2026-07-30T06:23:14.043", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}, {"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": "2025-07-25T15:15:28.707", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/890ba5be6335dbbbc99af14ea007befb5f83f174"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f8b1898748dfeb4f9b67b6a6d661f354b9de3523"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/fe30c30bf3bb68d4a4d8c7c814769857b5c973e6"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: Revert \"riscv: Define TASK_SIZE_MAX for __access_ok()\"", "id": "2383456", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2383456"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nRevert \"riscv: Define TASK_SIZE_MAX for __access_ok()\"\nThis reverts commit ad5643cf2f69 (\"riscv: Define TASK_SIZE_MAX for\n__access_ok()\").\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.\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.\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.\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].\nTherefore, revert this commit. TASK_SIZE_MAX is changed to the default:\nTASK_SIZE.\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."], "name": "CVE-2025-38434", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-07-25T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-38434\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-38434\nhttps://lore.kernel.org/linux-cve-announce/2025072512-CVE-2025-38434-ecdf@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-07-26T12:07:39.107898+00:00", "updated": "2025-07-26T12:07:39.107948+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}