tracing: Get trace_array ref counts when accessing trace files

commit 7b85af63 upstream.

When a trace file is opened that may access a trace array, it must
increment its ref count to prevent it from being deleted.
Reported-by: Alexander Lam <azl@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kernel/trace/trace.c

@@ -2902,6 +2902,43 @@ int tracing_open_generic(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+/*
+ * Open and update trace_array ref count.
+ * Must have the current trace_array passed to it.
+ */
+int tracing_open_generic_tr(struct inode *inode, struct file *filp)
+{
+	struct trace_array *tr = inode->i_private;
+
+	if (tracing_disabled)
+		return -ENODEV;
+
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
+
+	filp->private_data = inode->i_private;
+
+	return 0;
+
+}
+
+int tracing_open_generic_tc(struct inode *inode, struct file *filp)
+{
+	struct trace_cpu *tc = inode->i_private;
+	struct trace_array *tr = tc->tr;
+
+	if (tracing_disabled)
+		return -ENODEV;
+
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
+
+	filp->private_data = inode->i_private;
+
+	return 0;
+
+}
+
 static int tracing_release(struct inode *inode, struct file *file)
 {
 	struct seq_file *m = file->private_data;
@@ -2945,6 +2982,32 @@ static int tracing_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int tracing_release_generic_tr(struct inode *inode, struct file *file)
+{
+	struct trace_array *tr = inode->i_private;
+
+	trace_array_put(tr);
+	return 0;
+}
+
+static int tracing_release_generic_tc(struct inode *inode, struct file *file)
+{
+	struct trace_cpu *tc = inode->i_private;
+	struct trace_array *tr = tc->tr;
+
+	trace_array_put(tr);
+	return 0;
+}
+
+static int tracing_single_release_tr(struct inode *inode, struct file *file)
+{
+	struct trace_array *tr = inode->i_private;
+
+	trace_array_put(tr);
+
+	return single_release(inode, file);
+}
+
 static int tracing_open(struct inode *inode, struct file *file)
 {
 	struct trace_cpu *tc = inode->i_private;
@@ -3331,9 +3394,14 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 
 static int tracing_trace_options_open(struct inode *inode, struct file *file)
 {
+	struct trace_array *tr = inode->i_private;
+
 	if (tracing_disabled)
 		return -ENODEV;
 
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
+
 	return single_open(file, tracing_trace_options_show, inode->i_private);
 }
 
@@ -3341,7 +3409,7 @@ static const struct file_operations tracing_iter_fops = {
 	.open		= tracing_trace_options_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= single_release,
+	.release	= tracing_single_release_tr,
 	.write		= tracing_trace_options_write,
 };
 
@@ -3829,6 +3897,9 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 	if (tracing_disabled)
 		return -ENODEV;
 
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
+
 	mutex_lock(&trace_types_lock);
 
 	/* create a buffer to store the information to pass to userspace */
@@ -3881,6 +3952,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 fail:
 	kfree(iter->trace);
 	kfree(iter);
+	__trace_array_put(tr);
 	mutex_unlock(&trace_types_lock);
 	return ret;
 }
@@ -3888,6 +3960,8 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 static int tracing_release_pipe(struct inode *inode, struct file *file)
 {
 	struct trace_iterator *iter = file->private_data;
+	struct trace_cpu *tc = inode->i_private;
+	struct trace_array *tr = tc->tr;
 
 	mutex_lock(&trace_types_lock);
 
@@ -3901,6 +3975,8 @@ static int tracing_release_pipe(struct inode *inode, struct file *file)
 	kfree(iter->trace);
 	kfree(iter);
 
+	trace_array_put(tr);
+
 	return 0;
 }
 
@@ -4358,6 +4434,8 @@ tracing_free_buffer_release(struct inode *inode, struct file *filp)
 	/* resize the ring buffer to 0 */
 	tracing_resize_ring_buffer(tr, 0, RING_BUFFER_ALL_CPUS);
 
+	trace_array_put(tr);
+
 	return 0;
 }
 
@@ -4534,10 +4612,20 @@ static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
 
 static int tracing_clock_open(struct inode *inode, struct file *file)
 {
+	struct trace_array *tr = inode->i_private;
+	int ret;
+
 	if (tracing_disabled)
 		return -ENODEV;
 
-	return single_open(file, tracing_clock_show, inode->i_private);
+	if (trace_array_get(tr))
+		return -ENODEV;
+
+	ret = single_open(file, tracing_clock_show, inode->i_private);
+	if (ret < 0)
+		trace_array_put(tr);
+
+	return ret;
 }
 
 struct ftrace_buffer_info {
@@ -4733,34 +4821,38 @@ static const struct file_operations tracing_pipe_fops = {
 };
 
 static const struct file_operations tracing_entries_fops = {
-	.open		= tracing_open_generic,
+	.open		= tracing_open_generic_tc,
 	.read		= tracing_entries_read,
 	.write		= tracing_entries_write,
 	.llseek		= generic_file_llseek,
+	.release	= tracing_release_generic_tc,
 };
 
 static const struct file_operations tracing_total_entries_fops = {
-	.open		= tracing_open_generic,
+	.open		= tracing_open_generic_tr,
 	.read		= tracing_total_entries_read,
 	.llseek		= generic_file_llseek,
+	.release	= tracing_release_generic_tr,
 };
 
 static const struct file_operations tracing_free_buffer_fops = {
+	.open		= tracing_open_generic_tr,
 	.write		= tracing_free_buffer_write,
 	.release	= tracing_free_buffer_release,
 };
 
 static const struct file_operations tracing_mark_fops = {
-	.open		= tracing_open_generic,
+	.open		= tracing_open_generic_tr,
 	.write		= tracing_mark_write,
 	.llseek		= generic_file_llseek,
+	.release	= tracing_release_generic_tr,
 };
 
 static const struct file_operations trace_clock_fops = {
 	.open		= tracing_clock_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= single_release,
+	.release	= tracing_single_release_tr,
 	.write		= tracing_clock_write,
 };
 
@@ -4788,13 +4880,19 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
 	struct trace_cpu *tc = inode->i_private;
 	struct trace_array *tr = tc->tr;
 	struct ftrace_buffer_info *info;
+	int ret;
 
 	if (tracing_disabled)
 		return -ENODEV;
 
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
+
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
-	if (!info)
+	if (!info) {
+		trace_array_put(tr);
 		return -ENOMEM;
+	}
 
 	mutex_lock(&trace_types_lock);
 
@@ -4812,7 +4910,11 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
 
 	mutex_unlock(&trace_types_lock);
 
-	return nonseekable_open(inode, filp);
+	ret = nonseekable_open(inode, filp);
+	if (ret < 0)
+		trace_array_put(tr);
+
+	return ret;
 }
 
 static unsigned int
@@ -5707,9 +5809,10 @@ rb_simple_write(struct file *filp, const char __user *ubuf,
 }
 
 static const struct file_operations rb_simple_fops = {
-	.open		= tracing_open_generic,
+	.open		= tracing_open_generic_tr,
 	.read		= rb_simple_read,
 	.write		= rb_simple_write,
+	.release	= tracing_release_generic_tr,
 	.llseek		= default_llseek,
 };