tracing: Make sure the parsed string always terminates with '\0'

Always mark the parsed string with a terminated nul '\0' character. This removes
the need for the users to have to append the '\0' before using the parsed string.

Link: http://lkml.kernel.org/r/1516093350-12045-4-git-send-email-changbin.du@intel.comAcked-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NChangbin Du <changbin.du@intel.com>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -5015,7 +5015,6 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
 	parser = &iter->parser;
 	if (trace_parser_loaded(parser)) {
-		parser->buffer[parser->idx] = 0;
 		ftrace_match_records(iter->hash, parser->buffer, parser->idx);
 	}
 
@@ -5329,7 +5328,6 @@ ftrace_graph_release(struct inode *inode, struct file *file)
 		parser = &fgd->parser;
 
 		if (trace_parser_loaded((parser))) {
-			parser->buffer[parser->idx] = 0;
 			ret = ftrace_graph_set_hash(fgd->new_hash,
 						    parser->buffer);
 		}

kernel/trace/trace.c

@@ -530,8 +530,6 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
 		ubuf += ret;
 		cnt -= ret;
 
-		parser.buffer[parser.idx] = 0;
-
 		ret = -EINVAL;
 		if (kstrtoul(parser.buffer, 0, &val))
 			break;
@@ -1268,6 +1266,8 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 	} else if (parser->idx < parser->size - 1) {
 		parser->cont = true;
 		parser->buffer[parser->idx++] = ch;
+		/* Make sure the parsed string always terminates with '\0'. */
+		parser->buffer[parser->idx] = 0;
 	} else {
 		ret = -EINVAL;
 		goto out;

kernel/trace/trace_events.c

@@ -885,8 +885,6 @@ ftrace_event_write(struct file *file, const char __user *ubuf,
 		if (*parser.buffer == '!')
 			set = 0;
 
-		parser.buffer[parser.idx] = 0;
-
 		ret = ftrace_set_clr_event(tr, parser.buffer + !set, set);
 		if (ret)
 			goto out_put;