kernfs: Acquire kernfs_rwsem in kernfs_get_parent_dentry().

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.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250213145023.2820193-3-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 1358c21837f1a0fe1b109e39134e993d0ef83879..b9b16e97bff18960da9cd9824f80e05742264a94 100644 (file)
--- 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));
 }