tracing: Have option files inc the trace array ref count

The option files update the options for a given trace array. For an
instance, if the file is opened and the instance is deleted, reading or
writing to the file will cause a use after free.

Up the ref count of the trace_array when an option file is opened.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lore.kernel.org/all/[email protected]/

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Zheng Yejian <[email protected]>
Fixes: 8530dec63e ("tracing: Add tracing_check_open_get_tr()")
Tested-by: Linux Kernel Functional Testing <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

kernel/trace/trace.c

@@ -8988,12 +8988,33 @@ trace_options_write(struct file *filp, const char __user *ubuf, size_t cnt,
 	return cnt;
 }
 
+static int tracing_open_options(struct inode *inode, struct file *filp)
+{
+	struct trace_option_dentry *topt = inode->i_private;
+	int ret;
+
+	ret = tracing_check_open_get_tr(topt->tr);
+	if (ret)
+		return ret;
+
+	filp->private_data = inode->i_private;
+	return 0;
+}
+
+static int tracing_release_options(struct inode *inode, struct file *file)
+{
+	struct trace_option_dentry *topt = file->private_data;
+
+	trace_array_put(topt->tr);
+	return 0;
+}
 
 static const struct file_operations trace_options_fops = {
-	.open = tracing_open_generic,
+	.open = tracing_open_options,
 	.read = trace_options_read,
 	.write = trace_options_write,
 	.llseek	= generic_file_llseek,
+	.release = tracing_release_options,
 };
 
 /*