From: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date: Fri, 11 Oct 2019 21:56:57 +0000 (-0400)
Subject: ftrace: Get a reference counter for the trace_array on filter files
X-Git-Tag: v5.15~5309^2~9
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9ef16693aff8137faa21d16ffe65bb9832d24d71;p=platform%2Fkernel%2Flinux-starfive.git

ftrace: Get a reference counter for the trace_array on filter files

The ftrace set_ftrace_filter and set_ftrace_notrace files are specific for
an instance now. They need to take a reference to the instance otherwise
there could be a race between accessing the files and deleting the instance.

It wasn't until the :mod: caching where these file operations started
referencing the trace_array directly.

Cc: stable@vger.kernel.org
Fixes: 673feb9d76ab3 ("ftrace: Add :mod: caching infrastructure to trace_array")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 62a50bf..32c2eb1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3540,21 +3540,22 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
 	struct ftrace_hash *hash;
 	struct list_head *mod_head;
 	struct trace_array *tr = ops->private;
-	int ret = 0;
+	int ret = -ENOMEM;
 
 	ftrace_ops_init(ops);
 
 	if (unlikely(ftrace_disabled))
 		return -ENODEV;
 
+	if (tr && trace_array_get(tr) < 0)
+		return -ENODEV;
+
 	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter)
-		return -ENOMEM;
+		goto out;
 
-	if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) {
-		kfree(iter);
-		return -ENOMEM;
-	}
+	if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX))
+		goto out;
 
 	iter->ops = ops;
 	iter->flags = flag;
@@ -3584,13 +3585,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
 
 		if (!iter->hash) {
 			trace_parser_put(&iter->parser);
-			kfree(iter);
-			ret = -ENOMEM;
 			goto out_unlock;
 		}
 	} else
 		iter->hash = hash;
 
+	ret = 0;
+
 	if (file->f_mode & FMODE_READ) {
 		iter->pg = ftrace_pages_start;
 
@@ -3602,7 +3603,6 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
 			/* Failed */
 			free_ftrace_hash(iter->hash);
 			trace_parser_put(&iter->parser);
-			kfree(iter);
 		}
 	} else
 		file->private_data = iter;
@@ -3610,6 +3610,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
  out_unlock:
 	mutex_unlock(&ops->func_hash->regex_lock);
 
+ out:
+	if (ret) {
+		kfree(iter);
+		if (tr)
+			trace_array_put(tr);
+	}
+
 	return ret;
 }
 
@@ -5037,6 +5044,8 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
 	mutex_unlock(&iter->ops->func_hash->regex_lock);
 	free_ftrace_hash(iter->hash);
+	if (iter->tr)
+		trace_array_put(iter->tr);
 	kfree(iter);
 
 	return 0;