diff options
| -rw-r--r-- | fs/kernfs/mount.c | 33 |
1 files changed, 24 insertions, 9 deletions
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index d1f512b7bf86..f1cea282aae3 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -220,12 +220,19 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn, return dentry; root = kernfs_root(kn); - guard(rwsem_read)(&root->kernfs_rwsem); - - knparent = find_next_ancestor(kn, NULL); - if (WARN_ON(!knparent)) { - dput(dentry); + /* + * As long as kn is valid, its parent can not vanish. This is cgroup's + * kn so it not have its parent replaced. Therefore it is safe to use + * the ancestor node outside of the RCU or locked section. + */ + if (WARN_ON_ONCE(!(root->flags & KERNFS_ROOT_INVARIANT_PARENT))) return ERR_PTR(-EINVAL); + scoped_guard(rcu) { + knparent = find_next_ancestor(kn, NULL); + if (WARN_ON(!knparent)) { + dput(dentry); + return ERR_PTR(-EINVAL); + } } do { @@ -235,14 +242,22 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn, if (kn == knparent) return dentry; - kntmp = find_next_ancestor(kn, knparent); - if (WARN_ON(!kntmp)) { + + scoped_guard(rwsem_read, &root->kernfs_rwsem) { + kntmp = find_next_ancestor(kn, knparent); + if (WARN_ON(!kntmp)) { + dput(dentry); + return ERR_PTR(-EINVAL); + } + name = kstrdup(kernfs_rcu_name(kntmp), GFP_KERNEL); + } + if (!name) { dput(dentry); - return ERR_PTR(-EINVAL); + return ERR_PTR(-ENOMEM); } - name = rcu_dereference(kntmp->name); dtmp = lookup_positive_unlocked(name, dentry, strlen(name)); dput(dentry); + kfree(name); if (IS_ERR(dtmp)) return dtmp; knparent = kntmp; |