linux-kernel - Re: [PATCH] tracing/eprobe: Update cond flag before enabling trigger

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Message-ID: <20221118111940.1268da2b@gandalf.local.home>
Date:   Fri, 18 Nov 2022 11:19:40 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Rafael Mendonca <rafaelmendsr@...il.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@...il.com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH] tracing/eprobe: Update cond flag before enabling
 trigger

On Fri, 18 Nov 2022 10:34:40 -0300
Rafael Mendonca <rafaelmendsr@...il.com> wrote:

> It did not trigger the NULL pointer issue to be more specific. When
> creating event probe for all events I was unable to create any event for
> the xhci-hcd system:
> 
> root@...alhost:/sys/kernel/tracing# echo 'e xhci-hcd/xhci_add_endpoint' > dynamic_events 
> -bash: echo: write error: Invalid argument
> 
> Debugging the issue it seems that the problem is in the is_good_name()
> check, which returns false for "xhci-hcd". Should we sanitize it by

Ouch. I didn't realize that.

> converting '-' into '_'?

Actually, it's just the system name that's an issue. I tested this patch
and it appears to work.

-- Steve


diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 54ee5711c729..a16fb4c9642e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1955,17 +1955,30 @@ static __always_inline void trace_iterator_reset(struct trace_iterator *iter)
 }
 
 /* Check the name is good for event/group/fields */
-static inline bool is_good_name(const char *name)
+static inline bool __is_good_name(const char *name, bool hash_ok)
 {
-	if (!isalpha(*name) && *name != '_')
+	if (!isalpha(*name) && *name != '_' && (!hash_ok || *name != '-'))
 		return false;
 	while (*++name != '\0') {
-		if (!isalpha(*name) && !isdigit(*name) && *name != '_')
+		if (!isalpha(*name) && !isdigit(*name) && *name != '_' &&
+		    (!hash_ok || *name != '-'))
 			return false;
 	}
 	return true;
 }
 
+/* Check the name is good for event/group/fields */
+static inline bool is_good_name(const char *name)
+{
+	return __is_good_name(name, false);
+}
+
+/* Check the name is good for system */
+static inline bool is_good_system_name(const char *name)
+{
+	return __is_good_name(name, true);
+}
+
 /* Convert certain expected symbols into '_' when generating event names */
 static inline void sanitize_event_name(char *name)
 {
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 36dff277de46..bb2f95d7175c 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -246,7 +246,7 @@ int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
 			return -EINVAL;
 		}
 		strlcpy(buf, event, slash - event + 1);
-		if (!is_good_name(buf)) {
+		if (!is_good_system_name(buf)) {
 			trace_probe_log_err(offset, BAD_GROUP_NAME);
 			return -EINVAL;
 		}