tracing: Add missing helper functions in event pointer dereference check

The process_pointer() helper function looks to see if various trace event
macros are used. These macros are for storing data in the event. This
makes it safe to dereference as the dereference will then point into the
event on the ring buffer where the content of the data stays with the
event itself.

A few helper functions were missing. Those were:

  __get_rel_dynamic_array()
  __get_dynamic_array_len()
  __get_rel_dynamic_array_len()
  __get_rel_sockaddr()

Also add a helper function find_print_string() to not need to use a middle
man variable to test if the string exists.

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: 5013f45 ("tracing: Add check of trace event print fmts for dereferencing pointers")
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/trace_events.c

@@ -274,6 +274,15 @@ static bool test_field(const char *fmt, struct trace_event_call *call)
 	return false;
 }
 
+/* Look for a string within an argument */
+static bool find_print_string(const char *arg, const char *str, const char *end)
+{
+	const char *r;
+
+	r = strstr(arg, str);
+	return r && r < end;
+}
+
 /* Return true if the argument pointer is safe */
 static bool process_pointer(const char *fmt, int len, struct trace_event_call *call)
 {
@@ -292,9 +301,17 @@ static bool process_pointer(const char *fmt, int len, struct trace_event_call *c
 		a = strchr(fmt, '&');
 		if ((a && (a < r)) || test_field(r, call))
 			return true;
-	} else if ((r = strstr(fmt, "__get_dynamic_array(")) && r < e) {
+	} else if (find_print_string(fmt, "__get_dynamic_array(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_rel_dynamic_array(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_dynamic_array_len(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_rel_dynamic_array_len(", e)) {
+		return true;
+	} else if (find_print_string(fmt, "__get_sockaddr(", e)) {
 		return true;
-	} else if ((r = strstr(fmt, "__get_sockaddr(")) && r < e) {
+	} else if (find_print_string(fmt, "__get_rel_sockaddr(", e)) {
 		return true;
 	}
 	return false;