Commit 3a53acf1 authored by Prateek Sood's avatar Prateek Sood Committed by Steven Rostedt (VMware)
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tracing: Fix lock inversion in trace_event_enable_tgid_record() 

       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>
parent 106f41f5

kernel/trace/trace.c

+8 −0
Original line number Diff line number Diff line
@@ -4685,6 +4685,10 @@ int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set) 


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

{

	if ((mask == TRACE_ITER_RECORD_TGID) ||

	    (mask == TRACE_ITER_RECORD_CMD))

		lockdep_assert_held(&event_mutex);



	/* do nothing if flag is already set */

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

		return 0;
@@ -4752,6 +4756,7 @@ static int trace_set_options(struct trace_array *tr, char *option) 


	cmp += len;



	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);



	ret = match_string(trace_options, -1, cmp);
@@ -4762,6 +4767,7 @@ static int trace_set_options(struct trace_array *tr, char *option) 
		ret = set_tracer_flag(tr, 1 << ret, !neg);



	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);



	/*

	 * If the first trailing whitespace is replaced with '\0' by strstrip,
@@ -8076,9 +8082,11 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt, 
	if (val != 0 && val != 1)

		return -EINVAL;



	mutex_lock(&event_mutex);

	mutex_lock(&trace_types_lock);

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

	mutex_unlock(&trace_types_lock);

	mutex_unlock(&event_mutex);



	if (ret < 0)

		return ret;

kernel/trace/trace_events.c

+4 −4
Original line number Diff line number Diff line
@@ -320,7 +320,8 @@ void trace_event_enable_cmd_record(bool enable) 
	struct trace_event_file *file;

	struct trace_array *tr;



	mutex_lock(&event_mutex);

	lockdep_assert_held(&event_mutex);



	do_for_each_event_file(tr, file) {



		if (!(file->flags & EVENT_FILE_FL_ENABLED))
@@ -334,7 +335,6 @@ void trace_event_enable_cmd_record(bool enable) 
			clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);

		}

	} while_for_each_event_file();

	mutex_unlock(&event_mutex);

}



void trace_event_enable_tgid_record(bool enable)
@@ -342,7 +342,8 @@ void trace_event_enable_tgid_record(bool enable) 
	struct trace_event_file *file;

	struct trace_array *tr;



	mutex_lock(&event_mutex);

	lockdep_assert_held(&event_mutex);



	do_for_each_event_file(tr, file) {

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

			continue;
@@ -356,7 +357,6 @@ void trace_event_enable_tgid_record(bool enable) 
				  &file->flags);

		}

	} while_for_each_event_file();

	mutex_unlock(&event_mutex);

}



static int __ftrace_event_enable_disable(struct trace_event_file *file,

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