linux-kernel - [PATCH v3 06/17] rv: Use strings in da monitors tracepoints

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Message-ID: <20250715071434.22508-7-gmonaco@redhat.com>
Date: Tue, 15 Jul 2025 09:14:23 +0200
From: Gabriele Monaco <gmonaco@...hat.com>
To: linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-trace-kernel@...r.kernel.org
Cc: Gabriele Monaco <gmonaco@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Nam Cao <namcao@...utronix.de>,
	Tomas Glozar <tglozar@...hat.com>,
	Juri Lelli <jlelli@...hat.com>,
	Clark Williams <williams@...hat.com>,
	John Kacur <jkacur@...hat.com>
Subject: [PATCH v3 06/17] rv: Use strings in da monitors tracepoints

Using DA monitors tracepoints with KASAN enabled triggers the following
warning:

 BUG: KASAN: global-out-of-bounds in do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
 Read of size 32 at addr ffffffffaada8980 by task ...
 Call Trace:
  <TASK>
 [...]
  do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
  ? __pfx_do_trace_event_raw_event_event_da_monitor+0x10/0x10
  ? trace_event_sncid+0x83/0x200
  trace_event_sncid+0x163/0x200
 [...]
 The buggy address belongs to the variable:
  automaton_snep+0x4e0/0x5e0

This is caused by the tracepoints reading 32 bits __array instead of
__string from the automata definition. Such strings are literals and
reading 32 bytes ends up in out of bound memory accesses (e.g. the next
automaton's data in this case).
The error is harmless as, while printing the string, we stop at the null
terminator, but it should still be fixed.

Use the __string facilities while defining the tracepoints to avoid
reading out of bound memory.

Fixes: 792575348ff7 ("rv/include: Add deterministic automata monitor definition via C macros")
Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
---
 kernel/trace/rv/rv_trace.h | 76 +++++++++++++++++++-------------------
 1 file changed, 38 insertions(+), 38 deletions(-)

diff --git a/kernel/trace/rv/rv_trace.h b/kernel/trace/rv/rv_trace.h
index 17ba07329b670..d38e0d3abdfde 100644
--- a/kernel/trace/rv/rv_trace.h
+++ b/kernel/trace/rv/rv_trace.h
@@ -16,23 +16,23 @@ DECLARE_EVENT_CLASS(event_da_monitor,
 	TP_ARGS(state, event, next_state, final_state),
 
 	TP_STRUCT__entry(
-		__array(	char,	state,		MAX_DA_NAME_LEN	)
-		__array(	char,	event,		MAX_DA_NAME_LEN	)
-		__array(	char,	next_state,	MAX_DA_NAME_LEN	)
-		__field(	bool,	final_state			)
+		__string(	state,		state		)
+		__string(	event,		event		)
+		__string(	next_state,	next_state	)
+		__field(	bool,		final_state	)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->state,		state,		MAX_DA_NAME_LEN);
-		memcpy(__entry->event,		event,		MAX_DA_NAME_LEN);
-		memcpy(__entry->next_state,	next_state,	MAX_DA_NAME_LEN);
-		__entry->final_state		= final_state;
+		__assign_str(state);
+		__assign_str(event);
+		__assign_str(next_state);
+		__entry->final_state = final_state;
 	),
 
 	TP_printk("%s x %s -> %s%s",
-		__entry->state,
-		__entry->event,
-		__entry->next_state,
+		__get_str(state),
+		__get_str(event),
+		__get_str(next_state),
 		__entry->final_state ? " (final)" : "")
 );
 
@@ -43,18 +43,18 @@ DECLARE_EVENT_CLASS(error_da_monitor,
 	TP_ARGS(state, event),
 
 	TP_STRUCT__entry(
-		__array(	char,	state,		MAX_DA_NAME_LEN	)
-		__array(	char,	event,		MAX_DA_NAME_LEN	)
+		__string(	state,	state	)
+		__string(	event,	event	)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->state,		state,		MAX_DA_NAME_LEN);
-		memcpy(__entry->event,		event,		MAX_DA_NAME_LEN);
+		__assign_str(state);
+		__assign_str(event);
 	),
 
 	TP_printk("event %s not expected in the state %s",
-		__entry->event,
-		__entry->state)
+		__get_str(event),
+		__get_str(state))
 );
 
 #include <monitors/wip/wip_trace.h>
@@ -75,26 +75,26 @@ DECLARE_EVENT_CLASS(event_da_monitor_id,
 	TP_ARGS(id, state, event, next_state, final_state),
 
 	TP_STRUCT__entry(
-		__field(	int,	id				)
-		__array(	char,	state,		MAX_DA_NAME_LEN	)
-		__array(	char,	event,		MAX_DA_NAME_LEN	)
-		__array(	char,	next_state,	MAX_DA_NAME_LEN	)
-		__field(	bool,	final_state			)
+		__field(	int,		id		)
+		__string(	state,		state		)
+		__string(	event,		event		)
+		__string(	next_state,	next_state	)
+		__field(	bool,		final_state	)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->state,		state,		MAX_DA_NAME_LEN);
-		memcpy(__entry->event,		event,		MAX_DA_NAME_LEN);
-		memcpy(__entry->next_state,	next_state,	MAX_DA_NAME_LEN);
-		__entry->id			= id;
-		__entry->final_state		= final_state;
+		__assign_str(state);
+		__assign_str(event);
+		__assign_str(next_state);
+		__entry->id		= id;
+		__entry->final_state	= final_state;
 	),
 
 	TP_printk("%d: %s x %s -> %s%s",
 		__entry->id,
-		__entry->state,
-		__entry->event,
-		__entry->next_state,
+		__get_str(state),
+		__get_str(event),
+		__get_str(next_state),
 		__entry->final_state ? " (final)" : "")
 );
 
@@ -105,21 +105,21 @@ DECLARE_EVENT_CLASS(error_da_monitor_id,
 	TP_ARGS(id, state, event),
 
 	TP_STRUCT__entry(
-		__field(	int,	id				)
-		__array(	char,	state,		MAX_DA_NAME_LEN	)
-		__array(	char,	event,		MAX_DA_NAME_LEN	)
+		__field(	int,	id	)
+		__string(	state,	state	)
+		__string(	event,	event	)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->state,		state,		MAX_DA_NAME_LEN);
-		memcpy(__entry->event,		event,		MAX_DA_NAME_LEN);
-		__entry->id			= id;
+		__assign_str(state);
+		__assign_str(event);
+		__entry->id	= id;
 	),
 
 	TP_printk("%d: event %s not expected in the state %s",
 		__entry->id,
-		__entry->event,
-		__entry->state)
+		__get_str(event),
+		__get_str(state))
 );
 
 #include <monitors/wwnr/wwnr_trace.h>
-- 
2.50.1