linux-kernel - [PATCH] eventfs: Warn if an eventfs_inode is freed without is

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Message-ID: <20240131163700.2342a110@gandalf.local.home>
Date: Wed, 31 Jan 2024 16:37:00 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Linus Torvalds
 <torvalds@...ux-foundation.org>
Subject: [PATCH] eventfs: Warn if an eventfs_inode is freed without is_freed
 being set

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

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.

As put_ei() is also called on failure cases to free the ei, add a free_ei()
helper that sets the is_freed and then calls put_ei().

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 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 31cbe38739fa..463920295237 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)
@@ -684,7 +695,7 @@ 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;
@@ -775,7 +786,7 @@ 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);
 }
@@ -806,9 +817,8 @@ 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