CVE-2026-74636

Summary

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 notifier_call_chain+0x84/0x168 blocking_notifier_call_chain_robust+0x64/0xd4 load_module+0x10c8/0x123c __arm64_sys_finit_module+0x230/0x31c

Fix by taking event_mutex in trace_event_update_all() before trace_event_sem.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/4e39f7b4d9d36508c53e89e6cbc640728df870b5
• https://git.kernel.org/stable/c/a30d421468300b1e7b2f233136aeb2db8013f555
• https://git.kernel.org/stable/c/e5f1d301b4bdaa4206db251fdc691f623162b0a8
• https://git.kernel.org/stable/c/fdeb190b0905a6aaed1e5d6adfb8613214748d7d
• https://git.kernel.org/stable/c/ed49684e69f846bf50b5050651ccdb87cfd152c0
• https://git.kernel.org/stable/c/f128740f39ab28d1f4ad5bdd10f3e117eec0c374
• https://git.kernel.org/stable/c/c3730b8373bb5059d735509b9e6a00d7eb337d7c

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