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Commit af247192 authored by Prateek Sood's avatar Prateek Sood Committed by Greg Kroah-Hartman
Browse files

tracing: Fix lock inversion in trace_event_enable_tgid_record() 

commit 3a53acf1d9bea11b57c1f6205e3fe73f9d8a3688 upstream.

       Task T2                             Task T3
trace_options_core_write()            subsystem_open()

 mutex_lock(trace_types_lock)           mutex_lock(event_mutex)

 set_tracer_flag()

   trace_event_enable_tgid_record()       mutex_lock(trace_types_lock)

    mutex_lock(event_mutex)

This gives a circular dependency deadlock between trace_types_lock and
event_mutex. To fix this invert the usage of trace_types_lock and
event_mutex in trace_options_core_write(). This keeps the sequence of
lock usage consistent.

Link: http://lkml.kernel.org/r/0101016eef175e38-8ca71caf-a4eb-480d-a1e6-6f0bbc015495-000000@us-west-2.amazonses.com



Cc: stable@vger.kernel.org
Fixes: d914ba37 ("tracing: Add support for recording tgid of tasks")
Signed-off-by: default avatarPrateek Sood <prsood@codeaurora.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3444204d

kernel/trace/trace.c

+8 −0
Original line number Original line Diff line number Diff line
@@ -4368,6 +4368,10 @@ int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set) 




int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)

int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)

{

{

	if ((mask == TRACE_ITER_RECORD_TGID) ||

	    (mask == TRACE_ITER_RECORD_CMD))

		lockdep_assert_held(&event_mutex);



	/* do nothing if flag is already set */

	/* do nothing if flag is already set */

	if (!!(tr->trace_flags & mask) == !!enabled)

	if (!!(tr->trace_flags & mask) == !!enabled)

		return 0;

		return 0;
@@ -4433,6 +4437,7 @@ static int trace_set_options(struct trace_array *tr, char *option) 
		cmp += 2;

		cmp += 2;

	}

	}





	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);

	mutex_lock(&trace_types_lock);





	for (i = 0; trace_options[i]; i++) {

	for (i = 0; trace_options[i]; i++) {
@@ -4447,6 +4452,7 @@ static int trace_set_options(struct trace_array *tr, char *option) 
		ret = set_tracer_option(tr, cmp, neg);

		ret = set_tracer_option(tr, cmp, neg);





	mutex_unlock(&trace_types_lock);

	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);





	/*

	/*

	 * If the first trailing whitespace is replaced with '\0' by strstrip,

	 * If the first trailing whitespace is replaced with '\0' by strstrip,
@@ -7373,9 +7379,11 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt, 
	if (val != 0 && val != 1)

	if (val != 0 && val != 1)

		return -EINVAL;

		return -EINVAL;





	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);

	mutex_lock(&trace_types_lock);

	ret = set_tracer_flag(tr, 1 << index, val);

	ret = set_tracer_flag(tr, 1 << index, val);

	mutex_unlock(&trace_types_lock);

	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);





	if (ret < 0)

	if (ret < 0)

		return ret;

		return ret;

kernel/trace/trace_events.c

+4 −4
Original line number Original line Diff line number Diff line
@@ -326,7 +326,8 @@ void trace_event_enable_cmd_record(bool enable) 
	struct trace_event_file *file;

	struct trace_event_file *file;

	struct trace_array *tr;

	struct trace_array *tr;





	mutex_lock(&event_mutex);

	lockdep_assert_held(&event_mutex);



	do_for_each_event_file(tr, file) {

	do_for_each_event_file(tr, file) {





		if (!(file->flags & EVENT_FILE_FL_ENABLED))

		if (!(file->flags & EVENT_FILE_FL_ENABLED))
@@ -340,7 +341,6 @@ void trace_event_enable_cmd_record(bool enable) 
			clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);

			clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);

		}

		}

	} while_for_each_event_file();

	} while_for_each_event_file();

	mutex_unlock(&event_mutex);

}

}





void trace_event_enable_tgid_record(bool enable)

void trace_event_enable_tgid_record(bool enable)
@@ -348,7 +348,8 @@ void trace_event_enable_tgid_record(bool enable) 
	struct trace_event_file *file;

	struct trace_event_file *file;

	struct trace_array *tr;

	struct trace_array *tr;





	mutex_lock(&event_mutex);

	lockdep_assert_held(&event_mutex);



	do_for_each_event_file(tr, file) {

	do_for_each_event_file(tr, file) {

		if (!(file->flags & EVENT_FILE_FL_ENABLED))

		if (!(file->flags & EVENT_FILE_FL_ENABLED))

			continue;

			continue;
@@ -362,7 +363,6 @@ void trace_event_enable_tgid_record(bool enable) 
				  &file->flags);

				  &file->flags);

		}

		}

	} while_for_each_event_file();

	} while_for_each_event_file();

	mutex_unlock(&event_mutex);

}

}





static int __ftrace_event_enable_disable(struct trace_event_file *file,

static int __ftrace_event_enable_disable(struct trace_event_file *file,