[PATCH 5.10 077/135] tracing: Fix NULL pointer dereference in start_creating

[Greg Kroah-Hartman]

From: Kamal Agrawal <kamaagra@xxxxxxxxxxxxxx>

commit ff41c28c4b54052942180d8b3f49e75f1445135a upstream.

The event_trace_add_tracer() can fail. In this case, it leads to a crash
in start_creating with below call stack. Handle the error scenario
properly in trace_array_create_dir.

Call trace:
down_write+0x7c/0x204
start_creating.25017+0x6c/0x194
tracefs_create_file+0xc4/0x2b4
init_tracer_tracefs+0x5c/0x940
trace_array_create_dir+0x58/0xb4
trace_array_create+0x1bc/0x2b8
trace_array_get_by_name+0xdc/0x18c

Link: https://lkml.kernel.org/r/1627651386-21315-1-git-send-email-kamaagra@xxxxxxxxxxxxxx

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 4114fbfd02f1 ("tracing: Enable creating new instance early boot")
Signed-off-by: Kamal Agrawal <kamaagra@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/trace/trace.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8683,8 +8683,10 @@ static int trace_array_create_dir(struct
 		return -EINVAL;
 
 	ret = event_trace_add_tracer(tr->dir, tr);
-	if (ret)
+	if (ret) {
 		tracefs_remove(tr->dir);
+		return ret;
+	}
 
 	init_tracer_tracefs(tr, tr->dir);
 	__update_tracer_options(tr);