CVE-2024-49976

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> tracing/timerlat: Drop interface_lock in stop_kthread()<br /> <br /> stop_kthread() is the offline callback for "trace/osnoise:online", since<br /> commit 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing<br /> of kthread in stop_kthread()"), the following ABBA deadlock scenario is<br /> introduced:<br /> <br /> T1 | T2 [BP] | T3 [AP]<br /> osnoise_hotplug_workfn() | work_for_cpu_fn() | cpuhp_thread_fun()<br /> | _cpu_down() | osnoise_cpu_die()<br /> mutex_lock(&amp;interface_lock) | | stop_kthread()<br /> | cpus_write_lock() | mutex_lock(&amp;interface_lock)<br /> cpus_read_lock() | cpuhp_kick_ap() |<br /> <br /> As the interface_lock here in just for protecting the "kthread" field of<br /> the osn_var, use xchg() instead to fix this issue. Also use<br /> for_each_online_cpu() back in stop_per_cpu_kthreads() as it can take<br /> cpu_read_lock() again.