linux-kernel - [PATCH 3/7] tracing: Verify if trace array exists before destroying it.

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Date:   Mon, 29 Jul 2019 17:02:30 -0700
From:   Divya Indi <divya.indi@...cle.com>
To:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Cc:     Divya Indi <divya.indi@...cle.com>, Joe Jin <joe.jin@...cle.com>,
        Aruna Ramakrishna <aruna.ramakrishna@...cle.com>,
        Srinivas Eeda <srinivas.eeda@...cle.com>
Subject: [PATCH 3/7] tracing: Verify if trace array exists before destroying it.

A trace array can be destroyed from userspace or kernel. Verify if the
trace array exists before proceeding to destroy/remove it.

Signed-off-by: Divya Indi <divya.indi@...cle.com>
Reviewed-By: Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
---
 kernel/trace/trace.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1c80521..468ecc5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8421,17 +8421,27 @@ static int __remove_instance(struct trace_array *tr)
 	return 0;
 }
 
-int trace_array_destroy(struct trace_array *tr)
+int trace_array_destroy(struct trace_array *this_tr)
 {
+	struct trace_array *tr;
 	int ret;
 
-	if (!tr)
+	if (!this_tr) {
 		return -EINVAL;
+	}
 
 	mutex_lock(&event_mutex);
 	mutex_lock(&trace_types_lock);
 
-	ret = __remove_instance(tr);
+	ret = -ENODEV;
+
+	/* Making sure trace array exists before destroying it. */
+	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+		if (tr == this_tr) {
+			ret = __remove_instance(tr);
+			break;
+		}
+	}
 
 	mutex_unlock(&trace_types_lock);
 	mutex_unlock(&event_mutex);
-- 
1.8.3.1