[PATCH v4 2/6] kernfs: Acquire kernfs_rwsem in kernfs_get_parent_dentry().

[Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>]

kernfs_get_parent_dentry() passes kernfs_node::parent to
kernfs_get_inode().

Acquire kernfs_root::kernfs_rwsem to ensure kernfs_node::parent isn't
replaced during the operation.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 fs/kernfs/mount.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 1358c21837f1a..b9b16e97bff18 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -145,7 +145,9 @@ static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
 {
 	struct kernfs_node *kn = kernfs_dentry_node(child);
+	struct kernfs_root *root = kernfs_root(kn);
 
+	guard(rwsem_read)(&root->kernfs_rwsem);
 	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
 }
 
-- 
2.47.2