tracing: tprobe-events: Reject invalid tracepoint name

Commit 57a7e6d ("tracing/fprobe: Support raw tracepoints on
future loaded modules") allows user to set a tprobe on non-exist
tracepoint but it does not check the tracepoint name is acceptable.
So it leads tprobe has a wrong character for events (e.g. with
subsystem prefix). In this case, the event is not shown in the
events directory.

Reject such invalid tracepoint name.

The tracepoint name must consist of alphabet or digit or '_'.

Link: https://lore.kernel.org/all/174055073461.4079315.15875502830565214255.stgit@mhiramat.tok.corp.google.com/

Fixes: 57a7e6d ("tracing/fprobe: Support raw tracepoints on future loaded modules")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: stable@vger.kernel.org

Author: mhiramat

kernel/trace/trace_fprobe.c

@@ -1049,6 +1049,19 @@ static int parse_symbol_and_return(int argc, const char *argv[],
 	if (*is_return)
 		return 0;
 
+	if (is_tracepoint) {
+		tmp = *symbol;
+		while (*tmp && (isalnum(*tmp) || *tmp == '_'))
+			tmp++;
+		if (*tmp) {
+			/* find a wrong character. */
+			trace_probe_log_err(tmp - *symbol, BAD_TP_NAME);
+			kfree(*symbol);
+			*symbol = NULL;
+			return -EINVAL;
+		}
+	}
+
 	/* If there is $retval, this should be a return fprobe. */
 	for (i = 2; i < argc; i++) {
 		tmp = strstr(argv[i], "$retval");

kernel/trace/trace_probe.h

@@ -481,6 +481,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(NON_UNIQ_SYMBOL,	"The symbol is not unique"),		\
 	C(BAD_RETPROBE,		"Retprobe address must be an function entry"), \
 	C(NO_TRACEPOINT,	"Tracepoint is not found"),		\
+	C(BAD_TP_NAME,		"Invalid character in tracepoint name"),\
 	C(BAD_ADDR_SUFFIX,	"Invalid probed address suffix"), \
 	C(NO_GROUP_NAME,	"Group name is not specified"),		\
 	C(GROUP_TOO_LONG,	"Group name is too long"),		\