CVE-2025-39744
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: rcu: Fix rcu_read_unlock() deadloop due to IRQ work During rcu_read_unlock_special(), if this happens during irq_exit(), we can lockup if an IPI is issued. This is because the IPI itself triggers the irq_exit() path causing a recursive lock up. This is precisely what Xiongfeng found when invoking a BPF program on the trace_tick_stop() tracepoint As shown in the trace below. Fix by managing the irq_work state correctly. irq_exit() __irq_exit_rcu() /* in_hardirq() returns false after this */ preempt_count_sub(HARDIRQ_OFFSET) tick_irq_exit() tick_nohz_irq_exit() tick_nohz_stop_sched_tick() trace_tick_stop() /* a bpf prog is hooked on this trace point */ __bpf_trace_tick_stop() bpf_trace_run2() rcu_read_unlock_special() /* will send a IPI to itself */ irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu); A simple reproducer can also be obtained by doing the following in tick_irq_exit(). It will hang on boot without the patch: static inline void tick_irq_exit(void) { + rcu_read_lock(); + WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true); + rcu_read_unlock(); + [neeraj: Apply Frederic's suggested fix for PREEMPT_RT]
Severity
HIGH
CVSS score
7.1
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-11 17:15:37.600000
Last modified
2026-10-30 13:18:09.093000
View original CVE JSON
{
"id": "CVE-2025-39744",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-09-11T17:15:37.600",
"lastModified": "2026-10-30T13:18:09.093",
"vulnStatus": "Modified",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrcu: Fix rcu_read_unlock() deadloop due to IRQ work\n\nDuring rcu_read_unlock_special(), if this happens during irq_exit(), we\ncan lockup if an IPI is issued. This is because the IPI itself triggers\nthe irq_exit() path causing a recursive lock up.\n\nThis is precisely what Xiongfeng found when invoking a BPF program on\nthe trace_tick_stop() tracepoint As shown in the trace below. Fix by\nmanaging the irq_work state correctly.\n\nirq_exit()\n __irq_exit_rcu()\n /* in_hardirq() returns false after this */\n preempt_count_sub(HARDIRQ_OFFSET)\n tick_irq_exit()\n tick_nohz_irq_exit()\n\t tick_nohz_stop_sched_tick()\n\t trace_tick_stop() /* a bpf prog is hooked on this trace point */\n\t\t __bpf_trace_tick_stop()\n\t\t bpf_trace_run2()\n\t\t\t rcu_read_unlock_special()\n /* will send a IPI to itself */\n\t\t\t irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);\n\nA simple reproducer can also be obtained by doing the following in\ntick_irq_exit(). It will hang on boot without the patch:\n\n static inline void tick_irq_exit(void)\n {\n +\trcu_read_lock();\n +\tWRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);\n +\trcu_read_unlock();\n +\n\n[neeraj: Apply Frederic's suggested fix for PREEMPT_RT]"
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nrcu: Corrección del bucle muerto de rcu_read_unlock() debido al trabajo IRQ\n\nDurante rcu_read_unlock_special(), si esto ocurre durante irq_exit(), podemos bloquearnos si se emite un IPI. Esto se debe a que el propio IPI desencadena la ruta de irq_exit() causando un bloqueo recursivo.\n\nEsto es precisamente lo que Xiongfeng encontró al invocar un programa BPF en el punto de rastreo trace_tick_stop(). Como se muestra en el rastreo a continuación. Se corrige gestionando el estado de irq_work correctamente.\n\nirq_exit()\n __irq_exit_rcu()\n /* in_hardirq() devuelve falso después de esto */\n preempt_count_sub(HARDIRQ_OFFSET)\n tick_irq_exit()\n tick_nohz_irq_exit()\n\t tick_nohz_stop_sched_tick()\n\t trace_tick_stop() /* un programa bpf está enganchado a este punto de rastreo */\n\t\t __bpf_trace_tick_stop()\n\t\t bpf_trace_run2()\n\t\t\t rcu_read_unlock_special()\n /* enviará un IPI a sí mismo */\n\t\t\t irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);\n\nUn reproductor simple también se puede obtener haciendo lo siguiente en tick_irq_exit(). Se colgará al arrancar sin el parche:\n\n static inline void tick_irq_exit(void)\n {\n +\trcu_read_lock();\n +\tWRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);\n +\trcu_read_unlock();\n +\n\n[neeraj: Aplicar la corrección sugerida por Frederic para PREEMPT_RT]"
}
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"source": "[email protected]",
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"baseScore": 7.1,
"baseSeverity": "HIGH",
"attackVector": "LOCAL",
"attackComplexity": "LOW",
"privilegesRequired": "LOW",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"availabilityImpact": "HIGH"
},
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}
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"weaknesses": [
{
"source": "[email protected]",
"type": "Primary",
"description": [
{
"lang": "en",
"value": "CWE-125"
}
]
}
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