tracing: Fix NULL pointer dereference in start_creating

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@codeaurora.org
Cc: stable@vger.kernel.org
Fixes: 4114fbfd02f1 ("tracing: Enable creating new instance early boot")
Signed-off-by: Kamal Agrawal <kamaagra@codeaurora.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c59dd35..33899a7 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9135,8 +9135,10 @@ static int trace_array_create_dir(struct trace_array *tr)
                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);