[v6.6][PATCH 54/57] eventfs: Warn if an eventfs_inode is freed without is_freed being set

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

There should never be a case where an evenfs_inode is being freed without
is_freed being set. Add a WARN_ON_ONCE() if it ever happens. That would
mean there was one too many put_ei()s.

Link: https://lore.kernel.org/linux-trace-kernel/20240201161616.843551963@xxxxxxxxxxx

Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
(cherry picked from commit 5a49f996046ba947466bc7461e4b19c4d1daf978)
---
 fs/tracefs/event_inode.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 515fdace1eea..ca7daee7c811 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -73,6 +73,9 @@ enum {
 static void release_ei(struct kref *ref)
 {
 	struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
+
+	WARN_ON_ONCE(!ei->is_freed);
+
 	kfree(ei->entry_attrs);
 	kfree_const(ei->name);
 	kfree_rcu(ei, rcu);
@@ -84,6 +87,14 @@ static inline void put_ei(struct eventfs_inode *ei)
 		kref_put(&ei->kref, release_ei);
 }
 
+static inline void free_ei(struct eventfs_inode *ei)
+{
+	if (ei) {
+		ei->is_freed = 1;
+		put_ei(ei);
+	}
+}
+
 static inline struct eventfs_inode *get_ei(struct eventfs_inode *ei)
 {
 	if (ei)
@@ -679,7 +690,7 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode
 
 	/* Was the parent freed? */
 	if (list_empty(&ei->list)) {
-		put_ei(ei);
+		free_ei(ei);
 		ei = NULL;
 	}
 	return ei;
@@ -770,7 +781,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	return ei;
 
  fail:
-	put_ei(ei);
+	free_ei(ei);
 	tracefs_failed_creating(dentry);
 	return ERR_PTR(-ENOMEM);
 }
@@ -801,9 +812,8 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, int level)
 	list_for_each_entry(ei_child, &ei->children, list)
 		eventfs_remove_rec(ei_child, level + 1);
 
-	ei->is_freed = 1;
 	list_del(&ei->list);
-	put_ei(ei);
+	free_ei(ei);
 }
 
 /**
-- 
2.43.0