{"id":"AZL-70807","summary":"CVE-2025-39744 affecting package kernel 5.15.200.1-1","details":"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-\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's suggested fix for PREEMPT_RT]","modified":"2026-04-01T05:21:59.268224Z","published":"2025-09-11T17:15:37Z","upstream":["CVE-2025-39744"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39744"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"5.15.200.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-70807.json"}}],"schema_version":"1.7.5"}