Commit 85c9599b authored by Wei Li's avatar Wei Li Committed by Zheng Yejian
Browse files

tracing/timerlat: Drop interface_lock in stop_kthread() 

stable inclusion
from stable-v6.6.55
commit a4a05ceffe8fad68b45de38fe2311bda619e76e2
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRD5
CVE: CVE-2024-49976

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a4a05ceffe8fad68b45de38fe2311bda619e76e2

--------------------------------

commit b484a02c9cedf8703eff8f0756f94618004bd165 upstream.

stop_kthread() is the offline callback for "trace/osnoise:online", since
commit 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing
of kthread in stop_kthread()"), the following ABBA deadlock scenario is
introduced:

T1                            | T2 [BP]               | T3 [AP]
osnoise_hotplug_workfn()      | work_for_cpu_fn()     | cpuhp_thread_fun()
                              |   _cpu_down()         |   osnoise_cpu_die()
  mutex_lock(&interface_lock) |                       |     stop_kthread()
                              |     cpus_write_lock() |       mutex_lock(&interface_lock)
  cpus_read_lock()            |     cpuhp_kick_ap()   |

As the interface_lock here in just for protecting the "kthread" field of
the osn_var, use xchg() instead to fix this issue. Also use
for_each_online_cpu() back in stop_per_cpu_kthreads() as it can take
cpu_read_lock() again.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240924094515.3561410-3-liwei391@huawei.com


Fixes: 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()")
Signed-off-by: default avatarWei Li <liwei391@huawei.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZheng Yejian <zhengyejian1@huawei.com>
parent ed7fbeaf

kernel/trace/trace_osnoise.c

+6 −7
Original line number Diff line number Diff line
@@ -1953,12 +1953,8 @@ static void stop_kthread(unsigned int cpu) 
{

	struct task_struct *kthread;



	mutex_lock(&interface_lock);

	kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;

	kthread = xchg_relaxed(&(per_cpu(per_cpu_osnoise_var, cpu).kthread), NULL);

	if (kthread) {

		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;

		mutex_unlock(&interface_lock);



		if (cpumask_test_and_clear_cpu(cpu, &kthread_cpumask) &&

		    !WARN_ON(!test_bit(OSN_WORKLOAD, &osnoise_options))) {

			kthread_stop(kthread);
@@ -1972,7 +1968,6 @@ static void stop_kthread(unsigned int cpu) 
			put_task_struct(kthread);

		}

	} else {

		mutex_unlock(&interface_lock);

		/* if no workload, just return */

		if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {

			/*
@@ -1994,8 +1989,12 @@ static void stop_per_cpu_kthreads(void) 
{

	int cpu;



	for_each_possible_cpu(cpu)

	cpus_read_lock();



	for_each_online_cpu(cpu)

		stop_kthread(cpu);



	cpus_read_unlock();

}



/*