cve-2021-46939
Vulnerability from cvelistv5
Published
2024-02-27 18:40
Modified
2024-11-04 11:56
Severity ?
EPSS score ?
Summary
tracing: Restructure trace_clock_global() to never block
References
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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. 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