Patch "eventfs: Free all of the eventfs_inode after RCU" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    eventfs: Free all of the eventfs_inode after RCU

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     eventfs-free-all-of-the-eventfs_inode-after-rcu.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 02d6f1e22584272a0a121587a1ad7caae347b786
Author: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Date:   Thu May 2 16:08:22 2024 -0400

    eventfs: Free all of the eventfs_inode after RCU
    
    [ Upstream commit ee4e0379475e4fe723986ae96293e465014fa8d9 ]
    
    The freeing of eventfs_inode via a kfree_rcu() callback. But the content
    of the eventfs_inode was being freed after the last kref. This is
    dangerous, as changes are being made that can access the content of an
    eventfs_inode from an RCU loop.
    
    Instead of using kfree_rcu() use call_rcu() that calls a function to do
    all the freeing of the eventfs_inode after a RCU grace period has expired.
    
    Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.370261163@xxxxxxxxxxx
    
    Cc: stable@xxxxxxxxxxxxxxx
    Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
    Cc: Mark Rutland <mark.rutland@xxxxxxx>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
    Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Fixes: 43aa6f97c2d03 ("eventfs: Get rid of dentry pointers without refcounts")
    Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 57830b2bedb6d..db869e52aa5cc 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -73,6 +73,21 @@ enum {
 
 #define EVENTFS_MODE_MASK	(EVENTFS_SAVE_MODE - 1)
 
+static void free_ei_rcu(struct rcu_head *rcu)
+{
+	struct eventfs_inode *ei = container_of(rcu, struct eventfs_inode, rcu);
+	struct eventfs_root_inode *rei;
+
+	kfree(ei->entry_attrs);
+	kfree_const(ei->name);
+	if (ei->is_events) {
+		rei = get_root_inode(ei);
+		kfree(rei);
+	} else {
+		kfree(ei);
+	}
+}
+
 /*
  * eventfs_inode reference count management.
  *
@@ -85,7 +100,6 @@ static void release_ei(struct kref *ref)
 {
 	struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
 	const struct eventfs_entry *entry;
-	struct eventfs_root_inode *rei;
 
 	WARN_ON_ONCE(!ei->is_freed);
 
@@ -95,14 +109,7 @@ static void release_ei(struct kref *ref)
 			entry->release(entry->name, ei->data);
 	}
 
-	kfree(ei->entry_attrs);
-	kfree_const(ei->name);
-	if (ei->is_events) {
-		rei = get_root_inode(ei);
-		kfree_rcu(rei, ei.rcu);
-	} else {
-		kfree_rcu(ei, rcu);
-	}
+	call_rcu(&ei->rcu, free_ei_rcu);
 }
 
 static inline void put_ei(struct eventfs_inode *ei)