tracing: Change synthetic event string format to limit printed length

Change the format for printing synthetic field strings to limit the
length of the string printed even if it's not correctly terminated.

Link: https://lore.kernel.org/r/20201002210036.0200371b@oasis.local.home
Link: https://lkml.kernel.org/r/b6bdb34e70d970e8026daa3503db6b8e5cdad524.1601848695.git.zanussi@kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 24bc6d61aa4052d2777b39d4c5e33efbd324d97f..742ce5f62d6d5843bce6c6d703d37d9fff128ce6 100644 (file)
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -234,7 +234,7 @@ 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";
 
        return fmt;
 }
@@ -303,11 +303,13 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter,
                                str_field = (char *)entry + data_offset;
 
                                trace_seq_printf(s, print_fmt, se->fields[i]->name,
+                                                STR_VAR_LEN_MAX,
                                                 str_field,
                                                 i == se->n_fields - 1 ? "" : " ");
                                n_u64++;
                        } else {
                                trace_seq_printf(s, print_fmt, se->fields[i]->name,
+                                                STR_VAR_LEN_MAX,
                                                 (char *)&entry->fields[n_u64],
                                                 i == se->n_fields - 1 ? "" : " ");
                                n_u64 += STR_VAR_LEN_MAX / sizeof(u64);