linux-kernel - [PATCH V2] tracing/osnoise: Fix possible recursive locking for cpus_read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20250321095249.2739397-1-ranxiaokai627@163.com>
Date: Fri, 21 Mar 2025 09:52:49 +0000
From: Ran Xiaokai <ranxiaokai627@....com>
To: rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com,
	vishalc@...ux.ibm.com,
	bristot@...hat.com
Cc: stable@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	ran.xiaokai@....com.cn
Subject: [PATCH V2] tracing/osnoise: Fix possible recursive locking for cpus_read_lock()

From: Ran Xiaokai <ran.xiaokai@....com.cn>

Lockdep reports this deadlock log:

osnoise: could not start sampling thread
============================================
WARNING: possible recursive locking detected
--------------------------------------------
       CPU0
       ----
  lock(cpu_hotplug_lock);
  lock(cpu_hotplug_lock);

 Call Trace:
  <TASK>
  print_deadlock_bug+0x282/0x3c0
  __lock_acquire+0x1610/0x29a0
  lock_acquire+0xcb/0x2d0
  cpus_read_lock+0x49/0x120
  stop_per_cpu_kthreads+0x7/0x60
  start_kthread+0x103/0x120
  osnoise_hotplug_workfn+0x5e/0x90
  process_one_work+0x44f/0xb30
  worker_thread+0x33e/0x5e0
  kthread+0x206/0x3b0
  ret_from_fork+0x31/0x50
  ret_from_fork_asm+0x11/0x20
  </TASK>

This is the deadlock scenario:
osnoise_hotplug_workfn()
  guard(cpus_read_lock)();      // first lock call
  start_kthread(cpu)
    if (IS_ERR(kthread)) {
      stop_per_cpu_kthreads(); {
        cpus_read_lock();      // second lock call. Cause the AA deadlock
      }
    }

It is not necessary to call stop_per_cpu_kthreads() which stops osnoise
kthread for every other CPUs in the system if a failure occurs during
hotplug of a certain CPU.
For start_per_cpu_kthreads(), if the start_kthread() call fails,
this function calls stop_per_cpu_kthreads() to handle the error.
Therefore, similarly, there is no need to call stop_per_cpu_kthreads()
again within start_kthread().
So just remove stop_per_cpu_kthreads() from start_kthread to solve this issue.

Fixes: c8895e271f79 ("trace/osnoise: Support hotplug operations")
Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
---
 kernel/trace/trace_osnoise.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 647516a73fa2..e732c9e37e14 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2006,7 +2006,6 @@ static int start_kthread(unsigned int cpu)
 
 	if (IS_ERR(kthread)) {
 		pr_err(BANNER "could not start sampling thread\n");
-		stop_per_cpu_kthreads();
 		return -ENOMEM;
 	}
 
-- 
2.17.1