CVE-2025-39744 (GCVE-0-2025-39744)
Vulnerability from cvelistv5 – Published: 2025-09-11 16:52 – Updated: 2026-05-11 21:35
VLAI
EPSS
VEX
Title
rcu: Fix rcu_read_unlock() deadloop due to IRQ work
Summary
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
7.1 (High)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
0864f057b050bc6dd68106b3185e02db5140012d , < e7a375453cca2b8a0d2fa1b82b913f3fed7c0507
(git)
Affected: 0864f057b050bc6dd68106b3185e02db5140012d , < 1cfa244f7198d325594e627574930b7b91df5bfe (git) Affected: 0864f057b050bc6dd68106b3185e02db5140012d , < ddebb2a7677673cf4438a04e1a48b8ed6b0c8e9a (git) Affected: 0864f057b050bc6dd68106b3185e02db5140012d , < 56c5ef194f4509df63fc0f7a91ea5973ce479b1e (git) Affected: 0864f057b050bc6dd68106b3185e02db5140012d , < b41642c87716bbd09797b1e4ea7d904f06c39b7b (git) |
guessed | |
| Linux | Linux |
Affected:
5.3
Unaffected: 0 , < 5.3 (semver) Unaffected: 6.6.103 , ≤ 6.6.* (semver) Unaffected: 6.12.43 , ≤ 6.12.* (semver) Unaffected: 6.15.11 , ≤ 6.15.* (semver) Unaffected: 6.16.2 , ≤ 6.16.* (semver) Unaffected: 6.17 , ≤ * (original_commit_for_fix) |
guessed |
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"url": "https://git.kernel.org/stable/c/b41642c87716bbd09797b1e4ea7d904f06c39b7b"
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"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(\u0026rdp-\u003edefer_qs_iw, rdp-\u003ecpu);\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-\u003ercu_read_unlock_special.b.need_qs, true);\n +\trcu_read_unlock();\n +\n\n[neeraj: Apply Frederic\u0027s suggested fix for PREEMPT_RT]"
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"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nrcu: Correcci\u00f3n 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 encontr\u00f3 al invocar un programa BPF en el punto de rastreo trace_tick_stop(). Como se muestra en el rastreo a continuaci\u00f3n. Se corrige gestionando el estado de irq_work correctamente.\n\nirq_exit()\n __irq_exit_rcu()\n /* in_hardirq() devuelve falso despu\u00e9s 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 est\u00e1 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 /* enviar\u00e1 un IPI a s\u00ed mismo */\n\t\t\t irq_work_queue_on(\u0026rdp-\u003edefer_qs_iw, rdp-\u003ecpu);\n\nUn reproductor simple tambi\u00e9n se puede obtener haciendo lo siguiente en tick_irq_exit(). Se colgar\u00e1 al arrancar sin el parche:\n\n static inline void tick_irq_exit(void)\n {\n +\trcu_read_lock();\n +\tWRITE_ONCE(current-\u003ercu_read_unlock_special.b.need_qs, true);\n +\trcu_read_unlock();\n +\n\n[neeraj: Aplicar la correcci\u00f3n sugerida por Frederic para PREEMPT_RT]"
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"id": "CVE-2025-39744",
"lastModified": "2026-10-19T21:10:00.160",
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"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
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"redhat_vex": {
"aggregate_severity": "None",
"current_release_date": "2026-06-30T10:23:50+00:00",
"cve": "CVE-2025-39744",
"id": "CVE-2025-39744",
"initial_release_date": "2025-09-11T00:00:00+00:00",
"product_status:known_not_affected": "274",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: rcu: Fix rcu_read_unlock() deadloop due to IRQ work",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39744.json",
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}
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