tracing: Fix synth event printk format for str fields

The printk format for synth event uses "%.*s" to print string fields,
but then only passes the pointer part as var arg.

Replace %.*s with %s as the C string is guaranteed to be null-terminated.

The output in print fmt should never have been updated as __get_str()
handles the string limit because it can access the length of the string in
the string meta data that is saved in the ring buffer.

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Fixes: 8db4d6b ("tracing: Change synthetic event string format to limit printed length")
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Douglas Raillard <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: douglas-raillard-arm

kernel/trace/trace_events_synth.c

@@ -305,7 +305,7 @@ static const char *synth_field_fmt(char *type)
 	else if (strcmp(type, "gfp_t") == 0)
 		fmt = "%x";
 	else if (synth_field_is_string(type))
-		fmt = "%.*s";
+		fmt = "%s";
 	else if (synth_field_is_stack(type))
 		fmt = "%s";