CVE-2021-47566 (GCVE-0-2021-47566)

Vulnerability from cvelistv5 – Published: 2024-05-24 15:12 – Updated: 2026-05-11 13:57
VLAI
Title
proc/vmcore: fix clearing user buffer by properly using clear_user()
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.
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-06-12 19:44 UTC
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < a9e164bd160be8cbee1df70acb379129e3cd2e7c (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < 33a7d698f30fa0b99d50569e9909d3baa65d8f6a (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < 99d348b82bcb36171f24411d3f1a15706a2a937a (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < 9ef384ed300d1bcfb23d0ab0b487d544444d4b52 (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < fd7974c547abfb03072a4ee706d3a6f182266f89 (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < a8a917058faf4abaec9fb614bb6d5f8fe3529ec6 (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < 7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1 (git)
Affected: 997c136f518c5debd63847e78e2a8694f56dcf90 , < c1e63117711977cc4295b2ce73de29dd17066c82 (git)
Create a notification for this product.
Linux Linux Affected: 3.0
Unaffected: 0 , < 3.0 (semver)
Unaffected: 4.4.294 , ≤ 4.4.* (semver)
Unaffected: 4.9.292 , ≤ 4.9.* (semver)
Unaffected: 4.14.257 , ≤ 4.14.* (semver)
Unaffected: 4.19.219 , ≤ 4.19.* (semver)
Unaffected: 5.4.163 , ≤ 5.4.* (semver)
Unaffected: 5.10.83 , ≤ 5.10.* (semver)
Unaffected: 5.15.6 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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              "product": "Linux",
              "programFiles": [
                "fs/proc/vmcore.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "a9e164bd160b",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "33a7d698f30f",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "99d348b82bcb",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "9ef384ed300d",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "fd7974c547ab",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "a8a917058faf",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "7b3a34f08d11",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                },
                {
                  "lessThan": "c1e631177119",
                  "status": "affected",
                  "version": "997c136f518c",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "fs/proc/vmcore.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "3.0"
                },
                {
                  "lessThan": "3.0",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "4.4.*",
                  "status": "unaffected",
                  "version": "4.4.294",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "4.9.*",
                  "status": "unaffected",
                  "version": "4.9.292",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "4.14.*",
                  "status": "unaffected",
                  "version": "4.14.257",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "4.19.*",
                  "status": "unaffected",
                  "version": "4.19.219",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "5.4.*",
                  "status": "unaffected",
                  "version": "5.4.163",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "5.10.*",
                  "status": "unaffected",
                  "version": "5.10.83",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "5.15.*",
                  "status": "unaffected",
                  "version": "5.15.6",
                  "versionType": "custom"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "5.16",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "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."
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2024-05-29T05:10:14.234Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/a9e164bd160be8cbee1df70acb379129e3cd2e7c"
            },
            {
              "url": "https://git.kernel.org/stable/c/33a7d698f30fa0b99d50569e9909d3baa65d8f6a"
            },
            {
              "url": "https://git.kernel.org/stable/c/99d348b82bcb36171f24411d3f1a15706a2a937a"
            },
            {
              "url": "https://git.kernel.org/stable/c/9ef384ed300d1bcfb23d0ab0b487d544444d4b52"
            },
            {
              "url": "https://git.kernel.org/stable/c/fd7974c547abfb03072a4ee706d3a6f182266f89"
            },
            {
              "url": "https://git.kernel.org/stable/c/a8a917058faf4abaec9fb614bb6d5f8fe3529ec6"
            },
            {
              "url": "https://git.kernel.org/stable/c/7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1"
            },
            {
              "url": "https://git.kernel.org/stable/c/c1e63117711977cc4295b2ce73de29dd17066c82"
            }
          ],
          "title": "proc/vmcore: fix clearing user buffer by properly using clear_user()",
          "x_generator": {
            "engine": "bippy-a5840b7849dd"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2021-47566",
        "datePublished": "2024-05-24T15:12:53.432Z",
        "dateReserved": "2024-05-24T15:11:00.728Z",
        "dateUpdated": "2024-08-04T05:39:59.769Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



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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

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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.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


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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.