Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

[cascardo/linux.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index dcd9afe..58aca9c 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -27,6 +27,9 @@
 #include "pnode.h"
 #include "internal.h"
 
+/* Maximum number of mounts in a mount namespace */
+unsigned int sysctl_mount_max __read_mostly = 100000;
+
 static unsigned int m_hash_mask __read_mostly;
 static unsigned int m_hash_shift __read_mostly;
 static unsigned int mp_hash_mask __read_mostly;
@@ -899,6 +902,9 @@ static void commit_tree(struct mount *mnt, struct mount *shadows)
 
        list_splice(&head, n->list.prev);
 
+       n->mounts += n->pending_mounts;
+       n->pending_mounts = 0;
+
        attach_shadowed(mnt, parent, shadows);
        touch_mnt_namespace(n);
 }
@@ -1419,11 +1425,16 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
                propagate_umount(&tmp_list);
 
        while (!list_empty(&tmp_list)) {
+               struct mnt_namespace *ns;
                bool disconnect;
                p = list_first_entry(&tmp_list, struct mount, mnt_list);
                list_del_init(&p->mnt_expire);
                list_del_init(&p->mnt_list);
-               __touch_mnt_namespace(p->mnt_ns);
+               ns = p->mnt_ns;
+               if (ns) {
+                       ns->mounts--;
+                       __touch_mnt_namespace(ns);
+               }
                p->mnt_ns = NULL;
                if (how & UMOUNT_SYNC)
                        p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
@@ -1840,6 +1851,28 @@ static int invent_group_ids(struct mount *mnt, bool recurse)
        return 0;
 }
 
+int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
+{
+       unsigned int max = READ_ONCE(sysctl_mount_max);
+       unsigned int mounts = 0, old, pending, sum;
+       struct mount *p;
+
+       for (p = mnt; p; p = next_mnt(p, mnt))
+               mounts++;
+
+       old = ns->mounts;
+       pending = ns->pending_mounts;
+       sum = old + pending;
+       if ((old > sum) ||
+           (pending > sum) ||
+           (max < sum) ||
+           (mounts > (max - sum)))
+               return -ENOSPC;
+
+       ns->pending_mounts = pending + mounts;
+       return 0;
+}
+
 /*
  *  @source_mnt : mount tree to be attached
  *  @nd         : place the mount tree @source_mnt is attached
@@ -1909,10 +1942,18 @@ static int attach_recursive_mnt(struct mount *source_mnt,
                        struct path *parent_path)
 {
        HLIST_HEAD(tree_list);
+       struct mnt_namespace *ns = dest_mnt->mnt_ns;
        struct mount *child, *p;
        struct hlist_node *n;
        int err;
 
+       /* Is there space to add these mounts to the mount namespace? */
+       if (!parent_path) {
+               err = count_mounts(ns, source_mnt);
+               if (err)
+                       goto out;
+       }
+
        if (IS_MNT_SHARED(dest_mnt)) {
                err = invent_group_ids(source_mnt, true);
                if (err)
@@ -1949,11 +1990,13 @@ static int attach_recursive_mnt(struct mount *source_mnt,
  out_cleanup_ids:
        while (!hlist_empty(&tree_list)) {
                child = hlist_entry(tree_list.first, struct mount, mnt_hash);
+               child->mnt_parent->mnt_ns->pending_mounts = 0;
                umount_tree(child, UMOUNT_SYNC);
        }
        unlock_mount_hash();
        cleanup_group_ids(source_mnt, NULL);
  out:
+       ns->pending_mounts = 0;
        return err;
 }
 
@@ -2719,9 +2762,20 @@ dput_out:
        return retval;
 }
 
+static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
+{
+       return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
+}
+
+static void dec_mnt_namespaces(struct ucounts *ucounts)
+{
+       dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
+}
+
 static void free_mnt_ns(struct mnt_namespace *ns)
 {
        ns_free_inum(&ns->ns);
+       dec_mnt_namespaces(ns->ucounts);
        put_user_ns(ns->user_ns);
        kfree(ns);
 }
@@ -2738,14 +2792,22 @@ static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
 {
        struct mnt_namespace *new_ns;
+       struct ucounts *ucounts;
        int ret;
 
+       ucounts = inc_mnt_namespaces(user_ns);
+       if (!ucounts)
+               return ERR_PTR(-ENOSPC);
+
        new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
-       if (!new_ns)
+       if (!new_ns) {
+               dec_mnt_namespaces(ucounts);
                return ERR_PTR(-ENOMEM);
+       }
        ret = ns_alloc_inum(&new_ns->ns);
        if (ret) {
                kfree(new_ns);
+               dec_mnt_namespaces(ucounts);
                return ERR_PTR(ret);
        }
        new_ns->ns.ops = &mntns_operations;
@@ -2756,6 +2818,9 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
        init_waitqueue_head(&new_ns->poll);
        new_ns->event = 0;
        new_ns->user_ns = get_user_ns(user_ns);
+       new_ns->ucounts = ucounts;
+       new_ns->mounts = 0;
+       new_ns->pending_mounts = 0;
        return new_ns;
 }
 
@@ -2805,6 +2870,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
        q = new;
        while (p) {
                q->mnt_ns = new_ns;
+               new_ns->mounts++;
                if (new_fs) {
                        if (&p->mnt == new_fs->root.mnt) {
                                new_fs->root.mnt = mntget(&q->mnt);
@@ -2843,6 +2909,7 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
                struct mount *mnt = real_mount(m);
                mnt->mnt_ns = new_ns;
                new_ns->root = mnt;
+               new_ns->mounts++;
                list_add(&mnt->mnt_list, &new_ns->list);
        } else {
                mntput(m);
@@ -3348,10 +3415,16 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
        return 0;
 }
 
+static struct user_namespace *mntns_owner(struct ns_common *ns)
+{
+       return to_mnt_ns(ns)->user_ns;
+}
+
 const struct proc_ns_operations mntns_operations = {
        .name           = "mnt",
        .type           = CLONE_NEWNS,
        .get            = mntns_get,
        .put            = mntns_put,
        .install        = mntns_install,
+       .owner          = mntns_owner,
 };