nfsd: nfsd should drop CAP_MKNOD for non-root

[safe/jmp/linux-2.6] / fs / pnode.c

diff --git a/fs/pnode.c b/fs/pnode.c
index d18d664..8d5f392 100644 (file)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -28,6 +28,57 @@ static inline struct vfsmount *next_slave(struct vfsmount *p)
        return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
 }
 
+/*
+ * Return true if path is reachable from root
+ *
+ * namespace_sem is held, and mnt is attached
+ */
+static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
+                        const struct path *root)
+{
+       while (mnt != root->mnt && mnt->mnt_parent != mnt) {
+               dentry = mnt->mnt_mountpoint;
+               mnt = mnt->mnt_parent;
+       }
+       return mnt == root->mnt && is_subdir(dentry, root->dentry);
+}
+
+static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,
+                                           struct mnt_namespace *ns,
+                                           const struct path *root)
+{
+       struct vfsmount *m = mnt;
+
+       do {
+               /* Check the namespace first for optimization */
+               if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root))
+                       return m;
+
+               m = next_peer(m);
+       } while (m != mnt);
+
+       return NULL;
+}
+
+/*
+ * Get ID of closest dominating peer group having a representative
+ * under the given root.
+ *
+ * Caller must hold namespace_sem
+ */
+int get_dominating_id(struct vfsmount *mnt, const struct path *root)
+{
+       struct vfsmount *m;
+
+       for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
+               struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root);
+               if (d)
+                       return d->mnt_group_id;
+       }
+
+       return 0;
+}
+
 static int do_make_slave(struct vfsmount *mnt)
 {
        struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;