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
CWE
  • CWE-400 - Uncontrolled Resource Consumption
Assigner
References
Impacted products
Vendor Product Version
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)
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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      "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\"}, {\"lang\": \"es\", \"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\"}]",
      "id": "CVE-2021-46939",
      "lastModified": "2024-11-21T06:34:58.803",
      "metrics": "{\"cvssMetricV31\": [{\"source\": \"nvd@nist.gov\", \"type\": \"Primary\", \"cvssData\": {\"version\": \"3.1\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\", \"baseScore\": 5.5, \"baseSeverity\": \"MEDIUM\", \"attackVector\": \"LOCAL\", \"attackComplexity\": \"LOW\", \"privilegesRequired\": \"LOW\", \"userInteraction\": \"NONE\", \"scope\": \"UNCHANGED\", \"confidentialityImpact\": \"NONE\", \"integrityImpact\": \"NONE\", \"availabilityImpact\": \"HIGH\"}, \"exploitabilityScore\": 1.8, \"impactScore\": 3.6}]}",
      "published": "2024-02-27T19:04:05.873",
      "references": "[{\"url\": \"https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c\", \"source\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}, {\"url\": \"https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\"]}]",
      "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "vulnStatus": "Modified",
      "weaknesses": "[{\"source\": \"nvd@nist.gov\", \"type\": \"Primary\", \"description\": [{\"lang\": \"en\", \"value\": \"CWE-662\"}]}]"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2021-46939\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-02-27T19:04:05.873\",\"lastModified\":\"2025-04-22T16:15:19.423\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"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\"},{\"lang\":\"es\",\"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: 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\"versionType\": \"semver\", \"lessThanOrEqual\": \"4.14.*\"}, {\"status\": \"unaffected\", \"version\": \"4.19.191\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"4.19.*\"}, {\"status\": \"unaffected\", \"version\": \"5.4.118\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.36\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.11.20\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.11.*\"}, {\"status\": \"unaffected\", \"version\": \"5.12.3\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.12.*\"}, {\"status\": \"unaffected\", \"version\": \"5.13\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"kernel/trace/trace_clock.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4\"}, {\"url\": 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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\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.4.269\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.9.269\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.14.233\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.191\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.118\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.36\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.11.20\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.12.3\", \"versionStartIncluding\": \"2.6.30\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.13\", \"versionStartIncluding\": \"2.6.30\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-05-11T13:44:49.866Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-46939\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-11T13:44:49.866Z\", \"dateReserved\": \"2024-02-25T13:45:52.721Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-02-27T18:40:27.471Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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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.
  • 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.



Detection rules are retrieved from Rulezet.