Commit c94e45bc authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

tracing: Do not reference event data in post call triggers 



Trace event triggers can be called before or after the event has been
committed. If it has been called after the commit, there's a possibility
that the event no longer exists. Currently, the two post callers is the
trigger to disable tracing (traceoff) and the one that will record a stack
dump (stacktrace). Neither of them reference the trace event entry record,
as that would lead to a race condition that could pass in corrupted data.

To prevent any other users of the post data triggers from using the trace
event record, pass in NULL to the post call trigger functions for the event
record, as they should never need to use them in the first place.

This does not fix any bug, but prevents bugs from happening by new post call
trigger users.

Reviewed-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent f39e2391

include/linux/trace_events.h

+1 −2
Original line number Diff line number Diff line
@@ -435,8 +435,7 @@ event_triggers_call(struct trace_event_file *file, void *rec, 
		    struct ring_buffer_event *event);

extern void

event_triggers_post_call(struct trace_event_file *file,

			 enum event_trigger_type tt,

			 void *rec, struct ring_buffer_event *event);

			 enum event_trigger_type tt);



bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);

kernel/trace/trace.h

+2 −2
Original line number Diff line number Diff line
@@ -1334,7 +1334,7 @@ event_trigger_unlock_commit(struct trace_event_file *file, 
		trace_buffer_unlock_commit(file->tr, buffer, event, irq_flags, pc);



	if (tt)

		event_triggers_post_call(file, tt, entry, event);

		event_triggers_post_call(file, tt);

}



/**
@@ -1367,7 +1367,7 @@ event_trigger_unlock_commit_regs(struct trace_event_file *file, 
						irq_flags, pc, regs);



	if (tt)

		event_triggers_post_call(file, tt, entry, event);

		event_triggers_post_call(file, tt);

}



#define FILTER_PRED_INVALID	((unsigned short)-1)

kernel/trace/trace_events_trigger.c

+2 −4
Original line number Diff line number Diff line
@@ -97,7 +97,6 @@ EXPORT_SYMBOL_GPL(event_triggers_call); 
 * event_triggers_post_call - Call 'post_triggers' for a trace event

 * @file: The trace_event_file associated with the event

 * @tt: enum event_trigger_type containing a set bit for each trigger to invoke

 * @rec: The trace entry for the event

 *

 * For each trigger associated with an event, invoke the trigger

 * function registered with the associated trigger command, if the
@@ -108,8 +107,7 @@ EXPORT_SYMBOL_GPL(event_triggers_call); 
 */

void

event_triggers_post_call(struct trace_event_file *file,

			 enum event_trigger_type tt,

			 void *rec, struct ring_buffer_event *event)

			 enum event_trigger_type tt)

{

	struct event_trigger_data *data;
@@ -117,7 +115,7 @@ event_triggers_post_call(struct trace_event_file *file, 
		if (data->paused)

			continue;

		if (data->cmd_ops->trigger_type & tt)

			data->ops->func(data, rec, event);

			data->ops->func(data, NULL, NULL);

	}

}

EXPORT_SYMBOL_GPL(event_triggers_post_call);

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