linux-kernel - [PATCH 11/12] tracing: Use atomic_inc_return() for updating "disabled" counter in irqsoff tracer

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20250502205349.623319847@goodmis.org>
Date: Fri, 02 May 2025 16:51:58 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 11/12] tracing: Use atomic_inc_return() for updating "disabled" counter in
 irqsoff tracer

From: Steven Rostedt <rostedt@...dmis.org>

The irqsoff tracer uses the per CPU "disabled" field to prevent corruption
of the accounting when it starts to trace interrupts disabled, but there's
a slight race that could happen if for some reason it was called twice.
Use atomic_inc_return() instead.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_irqsoff.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 0b6d932a931e..5496758b6c76 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -397,6 +397,7 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip)
 	int cpu;
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
+	long disabled;
 
 	if (!tracer_enabled || !tracing_is_enabled())
 		return;
@@ -411,15 +412,17 @@ start_critical_timing(unsigned long ip, unsigned long parent_ip)
 	if (unlikely(!data) || local_read(&data->disabled))
 		return;
 
-	local_inc(&data->disabled);
+	disabled = local_inc_return(&data->disabled);
 
-	data->critical_sequence = max_sequence;
-	data->preempt_timestamp = ftrace_now(cpu);
-	data->critical_start = parent_ip ? : ip;
+	if (disabled == 1) {
+		data->critical_sequence = max_sequence;
+		data->preempt_timestamp = ftrace_now(cpu);
+		data->critical_start = parent_ip ? : ip;
 
-	__trace_function(tr, ip, parent_ip, tracing_gen_ctx());
+		__trace_function(tr, ip, parent_ip, tracing_gen_ctx());
 
-	per_cpu(tracing_cpu, cpu) = 1;
+		per_cpu(tracing_cpu, cpu) = 1;
+	}
 
 	local_dec(&data->disabled);
 }
@@ -431,6 +434,7 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 	struct trace_array *tr = irqsoff_trace;
 	struct trace_array_cpu *data;
 	unsigned int trace_ctx;
+	long disabled;
 
 	cpu = raw_smp_processor_id();
 	/* Always clear the tracing cpu on stopping the trace */
@@ -448,12 +452,15 @@ stop_critical_timing(unsigned long ip, unsigned long parent_ip)
 	    !data->critical_start || local_read(&data->disabled))
 		return;
 
-	local_inc(&data->disabled);
+	disabled = local_inc_return(&data->disabled);
+
+	if (disabled == 1) {
+		trace_ctx = tracing_gen_ctx();
+		__trace_function(tr, ip, parent_ip, trace_ctx);
+		check_critical_timing(tr, data, parent_ip ? : ip, cpu);
+		data->critical_start = 0;
+	}
 
-	trace_ctx = tracing_gen_ctx();
-	__trace_function(tr, ip, parent_ip, trace_ctx);
-	check_critical_timing(tr, data, parent_ip ? : ip, cpu);
-	data->critical_start = 0;
 	local_dec(&data->disabled);
 }
 
-- 
2.47.2