CVE-2021-46939 (GCVE-0-2021-46939)

Vulnerability from cvelistv5 – Published: 2024-02-27 18:40 – Updated: 2026-05-11 13:44
VLAI
Title
tracing: Restructure trace_clock_global() to never block
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Restructure trace_clock_global() to never block It was reported that a fix to the ring buffer recursion detection would cause a hung machine when performing suspend / resume testing. The following backtrace was extracted from debugging that case: Call Trace: trace_clock_global+0x91/0xa0 __rb_reserve_next+0x237/0x460 ring_buffer_lock_reserve+0x12a/0x3f0 trace_buffer_lock_reserve+0x10/0x50 __trace_graph_return+0x1f/0x80 trace_graph_return+0xb7/0xf0 ? trace_clock_global+0x91/0xa0 ftrace_return_to_handler+0x8b/0xf0 ? pv_hash+0xa0/0xa0 return_to_handler+0x15/0x30 ? ftrace_graph_caller+0xa0/0xa0 ? trace_clock_global+0x91/0xa0 ? __rb_reserve_next+0x237/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 ? trace_event_buffer_lock_reserve+0x3c/0x120 ? trace_event_buffer_reserve+0x6b/0xc0 ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0 ? dpm_run_callback+0x3b/0xc0 ? pm_ops_is_empty+0x50/0x50 ? platform_get_irq_byname_optional+0x90/0x90 ? trace_device_pm_callback_start+0x82/0xd0 ? dpm_run_callback+0x49/0xc0 With the following RIP: RIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200 Since the fix to the recursion detection would allow a single recursion to happen while tracing, this lead to the trace_clock_global() taking a spin lock and then trying to take it again: ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* lock taken */ (something else gets traced by function graph tracer) ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* DEAD LOCK! */ Tracing should *never* block, as it can lead to strange lockups like the above. Restructure the trace_clock_global() code to instead of simply taking a lock to update the recorded "prev_time" simply use it, as two events happening on two different CPUs that calls this at the same time, really doesn't matter which one goes first. Use a trylock to grab the lock for updating the prev_time, and if it fails, simply try again the next time. If it failed to be taken, that means something else is already updating it. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-04-22 16:06 UTC
CWE
  • CWE-400 - Uncontrolled Resource Consumption
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6665 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < 91ca6f6a91f679c8645d7f3307e03ce86ad518c4 (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < 859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < 1fca00920327be96f3318224f502e4d5460f9545 (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < d43d56dbf452ccecc1ec735cd4b6840118005d7c (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < c64da3294a7d59a4bf6874c664c13be892f15f44 (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < a33614d52e97fc8077eb0b292189ca7d964cc534 (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < 6e2418576228eeb12e7ba82edb8f9500623942ff (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < 2a1bd74b8186d7938bf004f5603f25b84785f63e (git)
Affected: 14131f2f98ac350ee9e73faed916d2238a8b6a0d , < aafe104aa9096827a429bc1358f8260ee565b7cc (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.30
Unaffected: 0 , < 2.6.30 (semver)
Unaffected: 4.4.269 , ≤ 4.4.* (semver)
Unaffected: 4.9.269 , ≤ 4.9.* (semver)
Unaffected: 4.14.233 , ≤ 4.14.* (semver)
Unaffected: 4.19.191 , ≤ 4.19.* (semver)
Unaffected: 5.4.118 , ≤ 5.4.* (semver)
Unaffected: 5.10.36 , ≤ 5.10.* (semver)
Unaffected: 5.11.20 , ≤ 5.11.* (semver)
Unaffected: 5.12.3 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
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            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: rastreo: reestructurar trace_clock_global() para no bloquear nunca. Se inform\u00f3 que una soluci\u00f3n a la detecci\u00f3n de recursividad del b\u00fafer circular provocar\u00eda que la m\u00e1quina se bloqueara al realizar pruebas de suspensi\u00f3n/reanudaci\u00f3n. El siguiente seguimiento se extrajo de la depuraci\u00f3n de ese caso: Call Trace: trace_clock_global+0x91/0xa0 __rb_reserve_next+0x237/0x460 ring_buffer_lock_reserve+0x12a/0x3f0 trace_buffer_lock_reserve+0x10/0x50 __trace_graph_return+0x1f/0x80 trace_graph_return+0xb7 /0xf0? trace_clock_global+0x91/0xa0 ftrace_return_to_handler+0x8b/0xf0 ? pv_hash+0xa0/0xa0 return_to_handler+0x15/0x30 ? ftrace_graph_caller+0xa0/0xa0? trace_clock_global+0x91/0xa0? __rb_reserve_next+0x237/0x460? ring_buffer_lock_reserve+0x12a/0x3f0? trace_event_buffer_lock_reserve+0x3c/0x120? trace_event_buffer_reserve+0x6b/0xc0? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0? dpm_run_callback+0x3b/0xc0? pm_ops_is_empty+0x50/0x50? platform_get_irq_byname_opcional+0x90/0x90? trace_device_pm_callback_start+0x82/0xd0? dpm_run_callback+0x49/0xc0 Con el siguiente RIP: RIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200 Dado que la soluci\u00f3n a la detecci\u00f3n de recursi\u00f3n permitir\u00eda que ocurriera una sola recursi\u00f3n durante el seguimiento, esto llev\u00f3 a trace_clock_global() a tomar un bloqueo de giro y luego intentarlo para tomarlo de nuevo: ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* bloqueo tomado */ (algo m\u00e1s es rastreado por la funci\u00f3n de seguimiento del gr\u00e1fico) ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath () { /* \u00a1BLOQUEO MUERTO! */ El rastreo *nunca* debe bloquearse, ya que puede provocar bloqueos extra\u00f1os como el anterior. Reestructura el c\u00f3digo trace_clock_global() para que, en lugar de simplemente tomar un bloqueo para actualizar el \"prev_time\" registrado, simplemente lo uses, ya que dos eventos suceden en dos CPU diferentes que llaman a esto al mismo tiempo, realmente no importa cu\u00e1l va primero. Utilice un trylock para obtener el bloqueo para actualizar prev_time y, si falla, simplemente int\u00e9ntelo de nuevo la pr\u00f3xima vez. Si no se pudo tomar, eso significa que algo m\u00e1s ya lo est\u00e1 actualizando. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761"
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                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2024-07-05T15:20:37.789Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "kernel/trace/trace_clock.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "91ca6f6a91f679c8645d7f3307e03ce86ad518c4",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "1fca00920327be96f3318224f502e4d5460f9545",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "d43d56dbf452ccecc1ec735cd4b6840118005d7c",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "c64da3294a7d59a4bf6874c664c13be892f15f44",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "a33614d52e97fc8077eb0b292189ca7d964cc534",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "6e2418576228eeb12e7ba82edb8f9500623942ff",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "2a1bd74b8186d7938bf004f5603f25b84785f63e",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                },
                {
                  "lessThan": "aafe104aa9096827a429bc1358f8260ee565b7cc",
                  "status": "affected",
                  "version": "14131f2f98ac350ee9e73faed916d2238a8b6a0d",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "kernel/trace/trace_clock.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "2.6.30"
                },
                {
                  "lessThan": "2.6.30",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "4.4.*",
                  "status": "unaffected",
                  "version": "4.4.269",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "4.9.*",
                  "status": "unaffected",
                  "version": "4.9.269",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "4.14.*",
                  "status": "unaffected",
                  "version": "4.14.233",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "4.19.*",
                  "status": "unaffected",
                  "version": "4.19.191",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.4.*",
                  "status": "unaffected",
                  "version": "5.4.118",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.10.*",
                  "status": "unaffected",
                  "version": "5.10.36",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.11.*",
                  "status": "unaffected",
                  "version": "5.11.20",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "5.12.*",
                  "status": "unaffected",
                  "version": "5.12.3",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "5.13",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "4.4.269",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "4.9.269",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "4.14.233",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "4.19.191",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.4.118",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.10.36",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.11.20",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.12.3",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.13",
                      "versionStartIncluding": "2.6.30",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Restructure trace_clock_global() to never block\n\nIt was reported that a fix to the ring buffer recursion detection would\ncause a hung machine when performing suspend / resume testing. The\nfollowing backtrace was extracted from debugging that case:\n\nCall Trace:\n trace_clock_global+0x91/0xa0\n __rb_reserve_next+0x237/0x460\n ring_buffer_lock_reserve+0x12a/0x3f0\n trace_buffer_lock_reserve+0x10/0x50\n __trace_graph_return+0x1f/0x80\n trace_graph_return+0xb7/0xf0\n ? trace_clock_global+0x91/0xa0\n ftrace_return_to_handler+0x8b/0xf0\n ? pv_hash+0xa0/0xa0\n return_to_handler+0x15/0x30\n ? ftrace_graph_caller+0xa0/0xa0\n ? trace_clock_global+0x91/0xa0\n ? __rb_reserve_next+0x237/0x460\n ? ring_buffer_lock_reserve+0x12a/0x3f0\n ? trace_event_buffer_lock_reserve+0x3c/0x120\n ? trace_event_buffer_reserve+0x6b/0xc0\n ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0\n ? dpm_run_callback+0x3b/0xc0\n ? pm_ops_is_empty+0x50/0x50\n ? platform_get_irq_byname_optional+0x90/0x90\n ? trace_device_pm_callback_start+0x82/0xd0\n ? dpm_run_callback+0x49/0xc0\n\nWith the following RIP:\n\nRIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200\n\nSince the fix to the recursion detection would allow a single recursion to\nhappen while tracing, this lead to the trace_clock_global() taking a spin\nlock and then trying to take it again:\n\nring_buffer_lock_reserve() {\n  trace_clock_global() {\n    arch_spin_lock() {\n      queued_spin_lock_slowpath() {\n        /* lock taken */\n        (something else gets traced by function graph tracer)\n          ring_buffer_lock_reserve() {\n            trace_clock_global() {\n              arch_spin_lock() {\n                queued_spin_lock_slowpath() {\n                /* DEAD LOCK! */\n\nTracing should *never* block, as it can lead to strange lockups like the\nabove.\n\nRestructure the trace_clock_global() code to instead of simply taking a\nlock to update the recorded \"prev_time\" simply use it, as two events\nhappening on two different CPUs that calls this at the same time, really\ndoesn\u0027t matter which one goes first. Use a trylock to grab the lock for\nupdating the prev_time, and if it fails, simply try again the next time.\nIf it failed to be taken, that means something else is already updating\nit.\n\n\nBugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761"
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-05-11T13:44:49.866Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4"
            },
            {
              "url": "https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b"
            },
            {
              "url": "https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545"
            },
            {
              "url": "https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c"
            },
            {
              "url": "https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44"
            },
            {
              "url": "https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534"
            },
            {
              "url": "https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff"
            },
            {
              "url": "https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e"
            },
            {
              "url": "https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc"
            }
          ],
          "title": "tracing: Restructure trace_clock_global() to never block",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2021-46939",
        "datePublished": "2024-02-27T18:40:27.471Z",
        "dateReserved": "2024-02-25T13:45:52.721Z",
        "dateUpdated": "2026-05-11T13:44:49.866Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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