CVE-2026-74636 — tracing: Fix race between update_event_fields and, event_define_fields

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

tracing: Fix race between update_event_fields and, event_define_fields

The following sequence may leads race between event_define_fields() and update_event_fields():

CPU0 (loads module A) CPU1 (loads module B) =============================== =============================== load_module(A) load_module(B) notifier_call_chain notifier_call_chain trace_module_notify trace_module_notify mutex_lock(&event_mutex) trace_event_update_all() trace_module_add_events(A) down_write(&trace_event_sem) __register_event(call_A) __add_event_to_tracers(call_A) event_define_fields(call_A) for each f: list_for_each_entry(field, list_add(&f->link, &class->fields, link) &class->fields) field = class->fields->next;

Where access to the class->fields is not protected by the event_mutex in trace_event_update_all().

This produces the following panic: Unable to handle kernel access ... at virtual address 0000000000000018 pc : update_event_fields+0xf8/0x368 Call trace: update_event_fields+0xf8/0x368 trace_event_update_all+0x7c/0x2b4 trace_module_notify+0x4c/0x1dc notifie…

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CVE-2026-74636 — tracing: Fix race between update_event_fields and, event_define_fields