[PATCH 5.16 0796/1039] tracing: Do not let synth_events block other dyn_event systems during create

[Greg Kroah-Hartman]

From: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit 4f67cca70c0f615e9cfe6ac42244f3416ec60877 ]

synth_events is returning -EINVAL if the dyn_event create command does
not contain ' \t'. This prevents other systems from getting called back.
synth_events needs to return -ECANCELED in these cases when the command
is not targeting the synth_event system.

Link: https://lore.kernel.org/linux-trace-devel/20210930223821.11025-1-beaub@xxxxxxxxxxxxxxxxxxx

Fixes: c9e759b1e8456 ("tracing: Rework synthetic event command parsing")
Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/trace/trace_events_synth.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index ca9c13b2ecf4b..4b5a637d3ec00 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -2054,6 +2054,13 @@ static int create_synth_event(const char *raw_command)
 
 	last_cmd_set(raw_command);
 
+	name = raw_command;
+
+	/* Don't try to process if not our system */
+	if (name[0] != 's' || name[1] != ':')
+		return -ECANCELED;
+	name += 2;
+
 	p = strpbrk(raw_command, " \t");
 	if (!p) {
 		synth_err(SYNTH_ERR_INVALID_CMD, 0);
@@ -2062,12 +2069,6 @@ static int create_synth_event(const char *raw_command)
 
 	fields = skip_spaces(p);
 
-	name = raw_command;
-
-	if (name[0] != 's' || name[1] != ':')
-		return -ECANCELED;
-	name += 2;
-
 	/* This interface accepts group name prefix */
 	if (strchr(name, '/')) {
 		len = str_has_prefix(name, SYNTH_SYSTEM "/");
-- 
2.34.1