linux-kernel - [PATCH 5.13 104/175] tracing: Fix NULL pointer dereference in start

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Date:   Tue, 10 Aug 2021 19:30:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kamal Agrawal <kamaagra@...eaurora.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 5.13 104/175] tracing: Fix NULL pointer dereference in start_creating

From: Kamal Agrawal <kamaagra@...eaurora.org>

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@codeaurora.org

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

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9006,8 +9006,10 @@ 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);