The patch below does not apply to the 6.8-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.8.y git checkout FETCH_HEAD git cherry-pick -x ee4e0379475e4fe723986ae96293e465014fa8d9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024051314-unwilling-outmatch-c624@gregkh' --subject-prefix 'PATCH 6.8.y' HEAD^..

Possible dependencies:

ee4e0379475e ("eventfs: Free all of the eventfs_inode after RCU") b63db58e2fa5 ("eventfs/tracing: Add callback for release of an eventfs_inode") c3137ab6318d ("eventfs: Create eventfs_root_inode to store dentry")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ee4e0379475e4fe723986ae96293e465014fa8d9 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" rostedt@goodmis.org Date: Thu, 2 May 2024 16:08:22 -0400 Subject: [PATCH] eventfs: Free all of the eventfs_inode after RCU

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@goodmis....

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Andrew Morton akpm@linux-foundation.org Fixes: 43aa6f97c2d03 ("eventfs: Get rid of dentry pointers without refcounts") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index f5510e26f0f6..cc8b838bbe62 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)