FKIE_CVE-2021-47566
Vulnerability from fkie_nvd - Published: 2024-05-24 15:15 - Updated: 2026-06-17 04:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
proc/vmcore: fix clearing user buffer by properly using clear_user()
To clear a user buffer we cannot simply use memset, we have to use
clear_user(). With a virtio-mem device that registers a vmcore_cb and
has some logically unplugged memory inside an added Linux memory block,
I can easily trigger a BUG by copying the vmcore via "cp":
systemd[1]: Starting Kdump Vmcore Save Service...
kdump[420]: Kdump is using the default log level(3).
kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/
kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/
kdump[465]: saving vmcore-dmesg.txt complete
kdump[467]: saving vmcore
BUG: unable to handle page fault for address: 00007f2374e01000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867
Oops: 0003 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014
RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86
Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81
RSP: 0018:ffffc9000073be08 EFLAGS: 00010212
RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000
RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008
RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50
R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000
R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8
FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0
Call Trace:
read_vmcore+0x236/0x2c0
proc_reg_read+0x55/0xa0
vfs_read+0x95/0x190
ksys_read+0x4f/0xc0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access
Prevention (SMAP)", which is used to detect wrong access from the kernel
to user buffers like this: SMAP triggers a permissions violation on
wrong access. In the x86-64 variant of clear_user(), SMAP is properly
handled via clac()+stac().
To fix, properly use clear_user() when we're dealing with a user buffer.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | 5.16 |
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{
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"status": "unaffected",
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},
{
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"status": "unaffected",
"version": "5.10.83",
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},
{
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"status": "unaffected",
"version": "5.15.6",
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},
{
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
}
]
}
],
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}
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"configurations": [
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],
"negate": false,
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],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nproc/vmcore: fix clearing user buffer by properly using clear_user()\n\nTo clear a user buffer we cannot simply use memset, we have to use\nclear_user(). With a virtio-mem device that registers a vmcore_cb and\nhas some logically unplugged memory inside an added Linux memory block,\nI can easily trigger a BUG by copying the vmcore via \"cp\":\n\n systemd[1]: Starting Kdump Vmcore Save Service...\n kdump[420]: Kdump is using the default log level(3).\n kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/\n kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/\n kdump[465]: saving vmcore-dmesg.txt complete\n kdump[467]: saving vmcore\n BUG: unable to handle page fault for address: 00007f2374e01000\n #PF: supervisor write access in kernel mode\n #PF: error_code(0x0003) - permissions violation\n PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867\n Oops: 0003 [#1] PREEMPT SMP NOPTI\n CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014\n RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86\n Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 \u003c49\u003e c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81\n RSP: 0018:ffffc9000073be08 EFLAGS: 00010212\n RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000\n RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008\n RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50\n R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000\n R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8\n FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000\n CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0\n Call Trace:\n read_vmcore+0x236/0x2c0\n proc_reg_read+0x55/0xa0\n vfs_read+0x95/0x190\n ksys_read+0x4f/0xc0\n do_syscall_64+0x3b/0x90\n entry_SYSCALL_64_after_hwframe+0x44/0xae\n\nSome x86-64 CPUs have a CPU feature called \"Supervisor Mode Access\nPrevention (SMAP)\", which is used to detect wrong access from the kernel\nto user buffers like this: SMAP triggers a permissions violation on\nwrong access. In the x86-64 variant of clear_user(), SMAP is properly\nhandled via clac()+stac().\n\nTo fix, properly use clear_user() when we\u0027re dealing with a user buffer."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: proc/vmcore: corrige el borrado del b\u00fafer del usuario usando correctamente clear_user() Para borrar un b\u00fafer de usuario no podemos simplemente usar memset, tenemos que usar clear_user(). Con un dispositivo virtio-mem que registra un vmcore_cb y tiene algo de memoria l\u00f3gicamente desconectada dentro de un bloque de memoria de Linux agregado, puedo desencadenar f\u00e1cilmente un ERROR copiando el vmcore a trav\u00e9s de \"cp\": systemd[1]: Iniciando el servicio Kdump Vmcore Save. . kdump[420]: Kdump est\u00e1 utilizando el nivel de registro predeterminado (3). kdump[453]: guardar en /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: guardar vmcore-dmesg.txt en /sysroot/var/crash/127.0 .0.1-2021-11-11-14:59:22/ kdump[465]: guardar vmcore-dmesg.txt completo kdump[467]: guardar vmcore ERROR: no se puede manejar el error de p\u00e1gina para la direcci\u00f3n: 00007f2374e01000 #PF: escritura del supervisor acceso en modo kernel #PF: error_code(0x0003) - violaci\u00f3n de permisos PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Ups: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: p No contaminado 5.15.0+ # 6 Nombre del hardware: PC est\u00e1ndar QEMU (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 01/04/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/ 0x86 C\u00f3digo: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 \u0026lt;49\u0026gt; c7 45 00 00 00 00 00 49 C7 44 05 F8 00 00 00 00 48 83 E7 F81 RSP: 0018: FFFFFC9000073BE08 EFLAGS: 00010212 RAX: 00000000000000001000 RBX: 000000002FD000 RCX: 00007F2374E RSI: 000000000000FFFFDFFF RDI: 00007F2374E01008 RBP: 000000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: 88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2 : 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Seguimiento de llamadas: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 do_syscall_64+0x3b/0x90 Entry_SYSCALL_64_after_hwframe+0x44/0xae Algunas CPU x86-64 tienen una funci\u00f3n de CPU llamada \"Prevenci\u00f3n de acceso en modo supervisor (SMAP)\", que se utiliza para detectar accesos incorrectos desde el kernel a los b\u00faferes de usuario como este: SMAP desencadena una violaci\u00f3n de permisos en caso de acceso incorrecto. En la variante x86-64 de clear_user(), SMAP se maneja correctamente mediante clac()+stac(). Para solucionarlo, utilice correctamente clear_user() cuando estemos tratando con un b\u00fafer de usuario."
}
],
"id": "CVE-2021-47566",
"lastModified": "2026-06-17T04:17:46.973",
"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": "nvd@nist.gov",
"type": "Primary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2021-47566",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2024-06-12T19:44:25.541373Z",
"version": "2.0.3"
}
}
]
},
"published": "2024-05-24T15:15:21.637",
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"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-787"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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