From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 13 Feb 2025 14:50:20 +0000 (+0100)
Subject: kernfs: Acquire kernfs_rwsem in kernfs_node_dentry().
X-Git-Tag: v6.15-rc1~79^2~51
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=5b2fabf7fe8f745ff214ff003e6067b64f172271;p=thirdparty%2Flinux.git

kernfs: Acquire kernfs_rwsem in kernfs_node_dentry().

kernfs_node_dentry() passes kernfs_node::name to
lookup_positive_unlocked().

Acquire kernfs_root::kernfs_rwsem to ensure the node is not renamed
during the operation.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250213145023.2820193-4-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index b9b16e97bff18..4a0ff08d589ca 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -209,6 +209,7 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 {
 	struct dentry *dentry;
 	struct kernfs_node *knparent;
+	struct kernfs_root *root;
 
 	BUG_ON(sb->s_op != &kernfs_sops);
 
@@ -218,6 +219,9 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 	if (!kn->parent)
 		return dentry;
 
+	root = kernfs_root(kn);
+	guard(rwsem_read)(&root->kernfs_rwsem);
+
 	knparent = find_next_ancestor(kn, NULL);
 	if (WARN_ON(!knparent)) {
 		dput(dentry);