Commit fd837de3 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google)
Browse files

tracing: probes: Fix a possible race in trace_probe_log APIs 

Since the shared trace_probe_log variable can be accessed and
modified via probe event create operation of kprobe_events,
uprobe_events, and dynamic_events, it should be protected.
In the dynamic_events, all operations are serialized by
`dyn_event_ops_mutex`. But kprobe_events and uprobe_events
interfaces are not serialized.

To solve this issue, introduces dyn_event_create(), which runs
create() operation under the mutex, for kprobe_events and
uprobe_events. This also uses lockdep to check the mutex is
held when using trace_probe_log* APIs.

Link: https://lore.kernel.org/all/174684868120.551552.3068655787654268804.stgit@devnote2/



Reported-by: default avatarPaul Cacheux <paulcacheux@gmail.com>
Closes: https://lore.kernel.org/all/20250510074456.805a16872b591e2971a4d221@kernel.org/


Fixes: ab105a4f ("tracing: Use tracing error_log with probe events")
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent e41b5af4

kernel/trace/trace_dynevent.c

+15 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ 
#include "trace_output.h"	/* for trace_event_sem */

#include "trace_dynevent.h"



static DEFINE_MUTEX(dyn_event_ops_mutex);

DEFINE_MUTEX(dyn_event_ops_mutex);

static LIST_HEAD(dyn_event_ops_list);



bool trace_event_dyn_try_get_ref(struct trace_event_call *dyn_call)
@@ -116,6 +116,20 @@ int dyn_event_release(const char *raw_command, struct dyn_event_operations *type 
	return ret;

}



/*

 * Locked version of event creation. The event creation must be protected by

 * dyn_event_ops_mutex because of protecting trace_probe_log.

 */

int dyn_event_create(const char *raw_command, struct dyn_event_operations *type)

{

	int ret;



	mutex_lock(&dyn_event_ops_mutex);

	ret = type->create(raw_command);

	mutex_unlock(&dyn_event_ops_mutex);

	return ret;

}



static int create_dyn_event(const char *raw_command)

{

	struct dyn_event_operations *ops;

kernel/trace/trace_dynevent.h

+1 −0
Original line number Diff line number Diff line
@@ -100,6 +100,7 @@ void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos); 
void dyn_event_seq_stop(struct seq_file *m, void *v);

int dyn_events_release_all(struct dyn_event_operations *type);

int dyn_event_release(const char *raw_command, struct dyn_event_operations *type);

int dyn_event_create(const char *raw_command, struct dyn_event_operations *type);



/*

 * for_each_dyn_event	-	iterate over the dyn_event list

kernel/trace/trace_kprobe.c

+1 −1
Original line number Diff line number Diff line
@@ -1089,7 +1089,7 @@ static int create_or_delete_trace_kprobe(const char *raw_command) 
	if (raw_command[0] == '-')

		return dyn_event_release(raw_command, &trace_kprobe_ops);



	ret = trace_kprobe_create(raw_command);

	ret = dyn_event_create(raw_command, &trace_kprobe_ops);

	return ret == -ECANCELED ? -EINVAL : ret;

}

kernel/trace/trace_probe.c

+9 −0
Original line number Diff line number Diff line
@@ -154,9 +154,12 @@ static const struct fetch_type *find_fetch_type(const char *type, unsigned long 
}



static struct trace_probe_log trace_probe_log;

extern struct mutex dyn_event_ops_mutex;



void trace_probe_log_init(const char *subsystem, int argc, const char **argv)

{

	lockdep_assert_held(&dyn_event_ops_mutex);



	trace_probe_log.subsystem = subsystem;

	trace_probe_log.argc = argc;

	trace_probe_log.argv = argv;
@@ -165,11 +168,15 @@ void trace_probe_log_init(const char *subsystem, int argc, const char **argv) 


void trace_probe_log_clear(void)

{

	lockdep_assert_held(&dyn_event_ops_mutex);



	memset(&trace_probe_log, 0, sizeof(trace_probe_log));

}



void trace_probe_log_set_index(int index)

{

	lockdep_assert_held(&dyn_event_ops_mutex);



	trace_probe_log.index = index;

}
@@ -178,6 +185,8 @@ void __trace_probe_log_err(int offset, int err_type) 
	char *command, *p;

	int i, len = 0, pos = 0;



	lockdep_assert_held(&dyn_event_ops_mutex);



	if (!trace_probe_log.argv)

		return;

kernel/trace/trace_uprobe.c

+1 −1
Original line number Diff line number Diff line
@@ -741,7 +741,7 @@ static int create_or_delete_trace_uprobe(const char *raw_command) 
	if (raw_command[0] == '-')

		return dyn_event_release(raw_command, &trace_uprobe_ops);



	ret = trace_uprobe_create(raw_command);

	ret = dyn_event_create(raw_command, &trace_uprobe_ops);

	return ret == -ECANCELED ? -EINVAL : ret;

}