linux-kernel - [PATCH v2] kprobes: Use synchronize_rcu_tasks_rude in kprobe

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Date: Thu, 18 Jan 2024 02:18:42 +0000
From: Chen Zhongjin <chenzhongjin@...wei.com>
To: <linux-kernel@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>
CC: <chenzhongjin@...wei.com>, <yangjihong1@...wei.com>,
	<naveen.n.rao@...ux.ibm.com>, <anil.s.keshavamurthy@...el.com>,
	<davem@...emloft.net>, <paulmck@...nel.org>, <mhiramat@...nel.org>,
	<akpm@...ux-foundation.org>, <tglx@...utronix.de>, <peterz@...radead.org>,
	<pmladek@...e.com>, <dianders@...omium.org>, <npiggin@...il.com>,
	<mpe@...erman.id.au>, <jkl820.git@...il.com>,
	<juerg.haefliger@...onical.com>, <rick.p.edgecombe@...el.com>,
	<eric.devolder@...cle.com>, <mic@...ikod.net>
Subject: [PATCH v2] kprobes: Use synchronize_rcu_tasks_rude in kprobe_optimizer

There is a deadlock scenario in kprobe_optimizer():

pid A				pid B			pid C
kprobe_optimizer()		do_exit()		perf_kprobe_init()
mutex_lock(&kprobe_mutex)	exit_tasks_rcu_start()	mutex_lock(&kprobe_mutex)
synchronize_rcu_tasks()		zap_pid_ns_processes()	// waiting kprobe_mutex
// waiting tasks_rcu_exit_srcu	kernel_wait4()
				// waiting pid C exit

To avoid this deadlock loop, use synchronize_rcu_tasks_rude() in kprobe_optimizer()
rather than synchronize_rcu_tasks(). synchronize_rcu_tasks_rude() can also promise
that all preempted tasks have scheduled, but it will not wait tasks_rcu_exit_srcu.

Fixes: a30b85df7d59 ("kprobes: Use synchronize_rcu_tasks() for optprobe with CONFIG_PREEMPT=y")
Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
---
v1 -> v2: Add Fixes tag
---
 arch/Kconfig     | 2 +-
 kernel/kprobes.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index f4b210ab0612..dc6a18854017 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -104,7 +104,7 @@ config STATIC_CALL_SELFTEST
 config OPTPROBES
 	def_bool y
 	depends on KPROBES && HAVE_OPTPROBES
-	select TASKS_RCU if PREEMPTION
+	select TASKS_RUDE_RCU
 
 config KPROBES_ON_FTRACE
 	def_bool y
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d5a0ee40bf66..09056ae50c58 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -623,7 +623,7 @@ static void kprobe_optimizer(struct work_struct *work)
 	 * Note that on non-preemptive kernel, this is transparently converted
 	 * to synchronoze_sched() to wait for all interrupts to have completed.
 	 */
-	synchronize_rcu_tasks();
+	synchronize_rcu_tasks_rude();
 
 	/* Step 3: Optimize kprobes after quiesence period */
 	do_optimize_kprobes();
-- 
2.25.1