diff options
Diffstat (limited to 'fs/kernfs/mount.c')
| -rw-r--r-- | fs/kernfs/mount.c | 44 |
1 files changed, 33 insertions, 11 deletions
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index 1358c21837f1..5124e196c2bf 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -145,8 +145,10 @@ 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); - return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent)); + guard(rwsem_read)(&root->kernfs_rwsem); + return d_obtain_alias(kernfs_get_inode(child->d_sb, kernfs_parent(kn))); } static const struct export_operations kernfs_export_ops = { @@ -186,10 +188,10 @@ static struct kernfs_node *find_next_ancestor(struct kernfs_node *child, return NULL; } - while (child->parent != parent) { - if (!child->parent) + while (kernfs_parent(child) != parent) { + child = kernfs_parent(child); + if (!child) return NULL; - child = child->parent; } return child; @@ -207,16 +209,27 @@ 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); dentry = dget(sb->s_root); /* Check if this is the root kernfs_node */ - if (!kn->parent) + if (!rcu_access_pointer(kn->__parent)) return dentry; - knparent = find_next_ancestor(kn, NULL); + root = kernfs_root(kn); + /* + * As long as kn is valid, its parent can not vanish. This is cgroup's + * kn so it can't 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); @@ -225,17 +238,26 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn, do { struct dentry *dtmp; struct kernfs_node *kntmp; + const char *name; 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); } - dtmp = lookup_positive_unlocked(kntmp->name, dentry, - strlen(kntmp->name)); + dtmp = lookup_positive_unlocked(name, dentry, strlen(name)); dput(dentry); + kfree(name); if (IS_ERR(dtmp)) return dtmp; knparent = kntmp; |