CVE-2021-47608

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["kernel/bpf/verifier.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "423628125a484538111c2c6d9bb1588eb086053b", "status": "affected", "version": "37086bfdc737ea6f66bf68dcf16757004d68e1e1", "versionType": "git"}, {"lessThan": "7d3baf0afa3aa9102d6a521a8e4c41888bb79882", "status": "affected", "version": "37086bfdc737ea6f66bf68dcf16757004d68e1e1", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["kernel/bpf/verifier.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.12"}, {"lessThan": "5.12", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.11", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "5.16", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "9E292CA0-C53B-4C70-B5CE-94AC1BC7673F", "versionEndExcluding": "5.15.11", "versionStartIncluding": "5.12", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:*", "matchCriteriaId": "357AA433-37E8-4323-BFB2-3038D6E4B414", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:*", "matchCriteriaId": "A73429BA-C2D9-4D0C-A75F-06A1CA8B3983", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:*", "matchCriteriaId": "F621B5E3-E99D-49E7-90B9-EC3B77C95383", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:*", "matchCriteriaId": "F7BFDCAA-1650-49AA-8462-407DD593F94F", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.16:rc5:*:*:*:*:*:*", "matchCriteriaId": "6EC9882F-866D-4ACB-8FBC-213D8D8436C8", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix kernel address leakage in atomic fetch\n\nThe change in commit 37086bfdc737 (\"bpf: Propagate stack bounds to registers\nin atomics w/ BPF_FETCH\") around check_mem_access() handling is buggy since\nthis would allow for unprivileged users to leak kernel pointers. For example,\nan atomic fetch/and with -1 on a stack destination which holds a spilled\npointer will migrate the spilled register type into a scalar, which can then\nbe exported out of the program (since scalar != pointer) by dumping it into\na map value.\n\nThe original implementation of XADD was preventing this situation by using\na double call to check_mem_access() one with BPF_READ and a subsequent one\nwith BPF_WRITE, in both cases passing -1 as a placeholder value instead of\nregister as per XADD semantics since it didn't contain a value fetch. The\nBPF_READ also included a check in check_stack_read_fixed_off() which rejects\nthe program if the stack slot is of __is_pointer_value() if dst_regno < 0.\nThe latter is to distinguish whether we're dealing with a regular stack spill/\nfill or some arithmetical operation which is disallowed on non-scalars, see\nalso 6e7e63cbb023 (\"bpf: Forbid XADD on spilled pointers for unprivileged\nusers\") for more context on check_mem_access() and its handling of placeholder\nvalue -1.\n\nOne minimally intrusive option to fix the leak is for the BPF_FETCH case to\ninitially check the BPF_READ case via check_mem_access() with -1 as register,\nfollowed by the actual load case with non-negative load_reg to propagate\nstack bounds to registers."}, {"lang": "es", "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: bpf: corrige la fuga de la direcci\u00f3n del kernel en la recuperaci\u00f3n at\u00f3mica. El cambio en el commit 37086bfdc737 (\"bpf: propaga los l\u00edmites de la pila a los registros en at\u00f3micos con BPF_FETCH\") alrededor del manejo de check_mem_access() tiene errores ya que esto permitir\u00eda a usuarios sin privilegios filtrar punteros del kernel. Por ejemplo, una recuperaci\u00f3n at\u00f3mica/y con -1 en un destino de pila que contiene un puntero derramado migrar\u00e1 el tipo de registro derramado a un escalar, que luego se puede exportar fuera del programa (ya que escalar! = puntero) volc\u00e1ndolo en un valor de mapa. La implementaci\u00f3n original de XADD evitaba esta situaci\u00f3n mediante el uso de una llamada doble a check_mem_access(), una con BPF_READ y otra posterior con BPF_WRITE, en ambos casos pasando -1 como valor de marcador de posici\u00f3n en lugar de registrarse seg\u00fan la sem\u00e1ntica de XADD, ya que no lo hac\u00eda contener una recuperaci\u00f3n de valor. BPF_READ tambi\u00e9n incluy\u00f3 una verificaci\u00f3n en check_stack_read_fixed_off() que rechaza el programa si la ranura de la pila es de __is_pointer_value() si dst_regno &lt; 0. Esto \u00faltimo es para distinguir si estamos tratando con un derrame/llenado de pila regular o alguna operaci\u00f3n aritm\u00e9tica que no est\u00e1 permitido en valores no escalares, consulte tambi\u00e9n 6e7e63cbb023 (\"bpf: Prohibir XADD en punteros dispersos para usuarios sin privilegios\") para obtener m\u00e1s contexto sobre check_mem_access() y su manejo del valor del marcador de posici\u00f3n -1. Una opci\u00f3n m\u00ednimamente intrusiva para solucionar la fuga es que el caso BPF_FETCH verifique inicialmente el caso BPF_READ mediante check_mem_access() con -1 como registro, seguido del caso de carga real con load_reg no negativo para propagar los l\u00edmites de la pila a los registros."}], "id": "CVE-2021-47608", "lastModified": "2026-06-17T04:18:09.287", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "NONE", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47608", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-09-10T17:12:01.674313Z", "version": "2.0.3"}}]}, "published": "2024-06-19T15:15:55.360", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/423628125a484538111c2c6d9bb1588eb086053b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7d3baf0afa3aa9102d6a521a8e4c41888bb79882"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/423628125a484538111c2c6d9bb1588eb086053b"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7d3baf0afa3aa9102d6a521a8e4c41888bb79882"}], "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: bpf: Fix kernel address leakage in atomic fetch", "id": "2293205", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2293205"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.4", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L", "status": "draft"}, "cwe": "CWE-200", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nbpf: Fix kernel address leakage in atomic fetch\nThe change in commit 37086bfdc737 (\"bpf: Propagate stack bounds to registers\nin atomics w/ BPF_FETCH\") around check_mem_access() handling is buggy since\nthis would allow for unprivileged users to leak kernel pointers. For example,\nan atomic fetch/and with -1 on a stack destination which holds a spilled\npointer will migrate the spilled register type into a scalar, which can then\nbe exported out of the program (since scalar != pointer) by dumping it into\na map value.\nThe original implementation of XADD was preventing this situation by using\na double call to check_mem_access() one with BPF_READ and a subsequent one\nwith BPF_WRITE, in both cases passing -1 as a placeholder value instead of\nregister as per XADD semantics since it didn't contain a value fetch. The\nBPF_READ also included a check in check_stack_read_fixed_off() which rejects\nthe program if the stack slot is of __is_pointer_value() if dst_regno < 0.\nThe latter is to distinguish whether we're dealing with a regular stack spill/\nfill or some arithmetical operation which is disallowed on non-scalars, see\nalso 6e7e63cbb023 (\"bpf: Forbid XADD on spilled pointers for unprivileged\nusers\") for more context on check_mem_access() and its handling of placeholder\nvalue -1.\nOne minimally intrusive option to fix the leak is for the BPF_FETCH case to\ninitially check the BPF_READ case via check_mem_access() with -1 as register,\nfollowed by the actual load case with non-negative load_reg to propagate\nstack bounds to registers."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2021-47608", "package_state": [{"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": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "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": "2024-06-19T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47608\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47608\nhttps://lore.kernel.org/linux-cve-announce/2024061924-CVE-2021-47608-f4eb@gregkh/T"], "threat_severity": "Low"}

{}