CVE-2021-47124

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[inline]\n io_put_req fs/io_uring.c:2140 [inline]\n io_queue_linked_timeout fs/io_uring.c:6300 [inline]\n __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354\n io_submit_sqe fs/io_uring.c:6534 [inline]\n io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660\n __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]\n __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182\n\nio_link_timeout_fn() should put only one reference of the linked timeout\nrequest, however in case of racing with the master request's completion\nfirst io_req_complete() puts one and then io_put_req_deferred() is\ncalled."}], "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 in io_uring's linked-timeout hrtimer path (io_link_timeout_fn), reached only via local io_uring_setup/io_uring_enter syscalls after submitting IORING_OP_LINK_TIMEOUT, not via network packet processing.\nAC:L - The race is between master-request completion and the linked-timeout hrtimer; the attacker controls both sides by choosing the linked operation and timeout duration and can retry until the double-put hits.\nPR:L - Any unprivileged local user can create an io_uring and submit linked timeouts; io_uring_setup has no CAP_SYS_ADMIN gate for this path (CAP_IPC_LOCK is only for locked-memory accounting).\nUI:N - Exploitation requires only the attacker's own io_uring submissions; no victim action such as mounting a filesystem or opening a crafted file is needed.\nS:U - A successful exploit yields corruption or control within the local kernel authority (typical local privilege escalation), not a cross-boundary escape such as guest-to-host or IOMMU bypass.\nC:H - The bug double-puts the linked-timeout io_kiocb (atomic_t refs, no saturation), freeing it then touching it again\u2014a use-after-free that can be reused for arbitrary kernel memory disclosure.\nI:H - Use-after-free of a slab-allocated io_kiocb enables heap reuse and write primitives suitable for control-flow hijacking or arbitrary kernel memory modification, as with related io_uring linked-timeout UAFs.\nA:H - The double-put underflows request refs and can free or corrupt the object while still in use, reliably causing kernel warnings, oopses, or crashes (and worse under exploitation)."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/io_uring.c"], "versions": [{"version": "1c20e9040f49687ba2ccc2ffd4411351a6c2ebff", "lessThan": "0b2a990e5d2f76d020cb840c456e6ec5f0c27530", "status": "affected", "versionType": "git"}, {"version": "1c20e9040f49687ba2ccc2ffd4411351a6c2ebff", "lessThan": "6f5d7a45f58d3abe3a936de1441b8d6318f978ff", "status": "affected", "versionType": "git"}, {"version": "9ae1f8dd372e0e4c020b345cf9e09f519265e981", "lessThan": 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refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28\nRIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28\nCall Trace:\n __refcount_sub_and_test include/linux/refcount.h:283 [inline]\n __refcount_dec_and_test include/linux/refcount.h:315 [inline]\n refcount_dec_and_test include/linux/refcount.h:333 [inline]\n io_put_req fs/io_uring.c:2140 [inline]\n io_queue_linked_timeout fs/io_uring.c:6300 [inline]\n __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354\n io_submit_sqe fs/io_uring.c:6534 [inline]\n io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660\n __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]\n __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182\n\nio_link_timeout_fn() should put only one reference of the linked timeout\nrequest, however in case of racing with the master request's completion\nfirst io_req_complete() puts one and then io_put_req_deferred() is\ncalled."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": 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"5.12.10", "versionType": "semver"}, {"lessThanOrEqual": "5.12.*", "status": "unaffected", "version": "5.12.19", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "5.13", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "7AA99340-AE0B-4861-BD12-24D20E28B7BD", "versionEndExcluding": "5.10.43", "versionStartIncluding": "5.10.26", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "6AF30DF1-E331-4DAC-B612-0FDA18281A08", "versionEndExcluding": "5.10.55", "versionStartIncluding": "5.10.44", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "C68A4290-9FFF-4037-9467-4FF878E3085F", "versionEndExcluding": "5.12.10", "versionStartIncluding": "5.12", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "FFAD6692-628C-40D7-A83C-01022B6D6DBA", "versionEndExcluding": "5.12.19", "versionStartIncluding": "5.12.11", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*", "matchCriteriaId": "0CBAD0FC-C281-4666-AB2F-F8E6E1165DF7", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: fix link timeout refs\n\nWARNING: CPU: 0 PID: 10242 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28\nRIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28\nCall Trace:\n __refcount_sub_and_test include/linux/refcount.h:283 [inline]\n __refcount_dec_and_test include/linux/refcount.h:315 [inline]\n refcount_dec_and_test include/linux/refcount.h:333 [inline]\n io_put_req fs/io_uring.c:2140 [inline]\n io_queue_linked_timeout fs/io_uring.c:6300 [inline]\n __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354\n io_submit_sqe fs/io_uring.c:6534 [inline]\n io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660\n __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]\n __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182\n\nio_link_timeout_fn() should put only one reference of the linked timeout\nrequest, however in case of racing with the master request's completion\nfirst io_req_complete() puts one and then io_put_req_deferred() is\ncalled."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: io_uring: corrige las referencias de tiempo de espera del enlace ADVERTENCIA: CPU: 0 PID: 10242 en lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28 RIP: 0010: refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28 Seguimiento de llamadas: __refcount_sub_and_test include/linux/refcount.h:283 [en l\u00ednea] __refcount_dec_and_test include/linux/refcount.h:315 [en l\u00ednea] refcount_dec_and_test include/linux/refcount.h: 333 [en l\u00ednea] io_put_req fs/io_uring.c:2140 [en l\u00ednea] io_queue_linked_timeout fs/io_uring.c:6300 [en l\u00ednea] __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354 io_submit_sqe fs/io_uring.c:6534 [en l\u00ednea] io_submit _sqes +0x2bbd/0x7c50 fs/io_uring.c:6660 __do_sys_io_uring_enter fs/io_uring.c:9240 [en l\u00ednea] __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182 io_link_timeout_fn() debe poner solo una referencia de la solicitud de tiempo de espera vinculada, sin embargo en En el caso de competir con la finalizaci\u00f3n de la solicitud maestra, primero io_req_complete() coloca uno y luego se llama a io_put_req_deferred()."}], "id": "CVE-2021-47124", "lastModified": "2026-08-04T10:16:47.023", "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"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47124", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-03-18T20:27:15.011125Z", "version": "2.0.3"}}]}, "published": "2024-03-15T21:15:07.260", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0b2a990e5d2f76d020cb840c456e6ec5f0c27530"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6f5d7a45f58d3abe3a936de1441b8d6318f978ff"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/876808dba2ff7509bdd7f230c4f374a0caf4f410"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a298232ee6b9a1d5d732aa497ff8be0d45b5bd82"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ff4a96ba5c8f9b266706280ff8021d2ef3f17e86"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0b2a990e5d2f76d020cb840c456e6ec5f0c27530"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6f5d7a45f58d3abe3a936de1441b8d6318f978ff"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/876808dba2ff7509bdd7f230c4f374a0caf4f410"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a298232ee6b9a1d5d732aa497ff8be0d45b5bd82"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ff4a96ba5c8f9b266706280ff8021d2ef3f17e86"}], "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: io_uring: fix link timeout refs", "id": "2269841", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2269841"}, "csaw": false, "cvss3": {"cvss3_base_score": "0.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:N", "status": "draft"}, "cwe": "CWE-20", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nio_uring: fix link timeout refs\nWARNING: CPU: 0 PID: 10242 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28\nRIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28\nCall Trace:\n__refcount_sub_and_test include/linux/refcount.h:283 [inline]\n__refcount_dec_and_test include/linux/refcount.h:315 [inline]\nrefcount_dec_and_test include/linux/refcount.h:333 [inline]\nio_put_req fs/io_uring.c:2140 [inline]\nio_queue_linked_timeout fs/io_uring.c:6300 [inline]\n__io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354\nio_submit_sqe fs/io_uring.c:6534 [inline]\nio_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660\n__do_sys_io_uring_enter fs/io_uring.c:9240 [inline]\n__se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182\nio_link_timeout_fn() should put only one reference of the linked timeout\nrequest, however in case of racing with the master request's completion\nfirst io_req_complete() puts one and then io_put_req_deferred() is\ncalled."], "name": "CVE-2021-47124", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "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": "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": "2024-03-15T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47124\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47124\nhttps://lore.kernel.org/linux-cve-announce/2024031511-CVE-2021-47124-42c9@gregkh/T/#u"], "threat_severity": "Low"}

{}