14 files changed, 105 insertions, 8 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 50ca17d3cb45..d581e45c0a9f 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -798,6 +798,10 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
         }
 
         mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
+        /* Don't allow unprivileged users to change mount flags */
+        if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
+                mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
+
         atomic_inc(&sb->s_active);
         mnt->mnt.mnt_sb = sb;
         mnt->mnt.mnt_root = dget(root);
@@ -1713,6 +1717,9 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
         if (readonly_request == __mnt_is_readonly(mnt))
                 return 0;
 
+        if (mnt->mnt_flags & MNT_LOCK_READONLY)
+                return -EPERM;
+
         if (readonly_request)
                 error = mnt_make_readonly(real_mount(mnt));
         else
@@ -2339,7 +2346,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
         /* First pass: copy the tree topology */
         copy_flags = CL_COPY_ALL | CL_EXPIRE;
         if (user_ns != mnt_ns->user_ns)
-                copy_flags |= CL_SHARED_TO_SLAVE;
+                copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
         new = copy_tree(old, old->mnt.mnt_root, copy_flags);
         if (IS_ERR(new)) {
                 up_write(&namespace_sem);
@@ -2732,6 +2739,51 @@ bool our_mnt(struct vfsmount *mnt)
         return check_mnt(real_mount(mnt));
 }
 
+bool current_chrooted(void)
+{
+        /* Does the current process have a non-standard root */
+        struct path ns_root;
+        struct path fs_root;
+        bool chrooted;
+
+        /* Find the namespace root */
+        ns_root.mnt = &current->nsproxy->mnt_ns->root->mnt;
+        ns_root.dentry = ns_root.mnt->mnt_root;
+        path_get(&ns_root);
+        while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
+                ;
+
+        get_fs_root(current->fs, &fs_root);
+
+        chrooted = !path_equal(&fs_root, &ns_root);
+
+        path_put(&fs_root);
+        path_put(&ns_root);
+
+        return chrooted;
+}
+
+void update_mnt_policy(struct user_namespace *userns)
+{
+        struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+        struct mount *mnt;
+
+        down_read(&namespace_sem);
+        list_for_each_entry(mnt, &ns->list, mnt_list) {
+                switch (mnt->mnt.mnt_sb->s_magic) {
+                case SYSFS_MAGIC:
+                        userns->may_mount_sysfs = true;
+                        break;
+                case PROC_SUPER_MAGIC:
+                        userns->may_mount_proc = true;
+                        break;
+                }
+                if (userns->may_mount_sysfs && userns->may_mount_proc)
+                        break;
+        }
+        up_read(&namespace_sem);
+}
+
 static void *mntns_get(struct task_struct *task)
 {
         struct mnt_namespace *ns = NULL;
diff --git a/fs/pnode.c b/fs/pnode.c
index 3e000a51ac0d..8b29d2164da6 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -9,6 +9,7 @@
 #include <linux/mnt_namespace.h>
 #include <linux/mount.h>
 #include <linux/fs.h>
+#include <linux/nsproxy.h>
 #include "internal.h"
 #include "pnode.h"
 
@@ -220,6 +221,7 @@ static struct mount *get_source(struct mount *dest,
 int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
                     struct mount *source_mnt, struct list_head *tree_list)
 {
+        struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
         struct mount *m, *child;
         int ret = 0;
         struct mount *prev_dest_mnt = dest_mnt;
@@ -237,6 +239,10 @@ int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
 
                 source =  get_source(m, prev_dest_mnt, prev_src_mnt, &type);
 
+                /* Notice when we are propagating across user namespaces */
+                if (m->mnt_ns->user_ns != user_ns)
+                        type |= CL_UNPRIVILEGED;
+
                 child = copy_tree(source, source->mnt.mnt_root, type);
                 if (IS_ERR(child)) {
                         ret = PTR_ERR(child);
diff --git a/fs/pnode.h b/fs/pnode.h
index 19b853a3445c..a0493d5ebfbf 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -23,6 +23,7 @@
 #define CL_MAKE_SHARED          0x08
 #define CL_PRIVATE              0x10
 #define CL_SHARED_TO_SLAVE      0x20
+#define CL_UNPRIVILEGED         0x40
 
 static inline void set_mnt_shared(struct mount *mnt)
 {
diff --git a/fs/proc/root.c b/fs/proc/root.c
index c6e9fac26bac..9c7fab1d23f0 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -16,6 +16,7 @@
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/bitops.h>
+#include <linux/user_namespace.h>
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
 #include <linux/parser.h>
@@ -108,6 +109,9 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
         } else {
                 ns = task_active_pid_ns(current);
                 options = data;
+
+                if (!current_user_ns()->may_mount_proc)
+                        return ERR_PTR(-EPERM);
         }
 
         sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8d924b5ec733..afd83273e6ce 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -19,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/magic.h>
 #include <linux/slab.h>
+#include <linux/user_namespace.h>
 
 #include "sysfs.h"
 
@@ -111,6 +112,9 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
         struct super_block *sb;
         int error;
 
+        if (!(flags & MS_KERNMOUNT) && !current_user_ns()->may_mount_sysfs)
+                return ERR_PTR(-EPERM);
+
         info = kzalloc(sizeof(*info), GFP_KERNEL);
         if (!info)
                 return ERR_PTR(-ENOMEM);
diff --git a/include/linux/fs_struct.h b/include/linux/fs_struct.h
index 729eded4b24f..2b93a9a5a1e6 100644
--- a/include/linux/fs_struct.h
+++ b/include/linux/fs_struct.h
@@ -50,4 +50,6 @@ static inline void get_fs_root_and_pwd(struct fs_struct *fs, struct path *root,
         spin_unlock(&fs->lock);
 }
 
+extern bool current_chrooted(void);
+
 #endif /* _LINUX_FS_STRUCT_H */
diff --git a/include/linux/mount.h b/include/linux/mount.h
index d7029f4a191a..73005f9957ea 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -47,6 +47,8 @@ struct mnt_namespace;
 
 #define MNT_INTERNAL    0x4000
 
+#define MNT_LOCK_READONLY       0x400000
+
 struct vfsmount {
         struct dentry *mnt_root;        /* root of the mounted tree */
         struct super_block *mnt_sb;     /* pointer to superblock */
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 4ce009324933..b6b215f13b45 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -26,6 +26,8 @@ struct user_namespace {
         kuid_t                  owner;
         kgid_t                  group;
         unsigned int            proc_inum;
+        bool                    may_mount_sysfs;
+        bool                    may_mount_proc;
 };
 
 extern struct user_namespace init_user_ns;
@@ -82,4 +84,6 @@ static inline void put_user_ns(struct user_namespace *ns)
 
 #endif
 
+void update_mnt_policy(struct user_namespace *userns);
+
 #endif /* _LINUX_USER_H */
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 3953fda2e8bd..e4e47f647446 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -330,8 +330,16 @@ static struct dentry *mqueue_mount(struct file_system_type *fs_type,
                          int flags, const char *dev_name,
                          void *data)
 {
-        if (!(flags & MS_KERNMOUNT))
-                data = current->nsproxy->ipc_ns;
+        if (!(flags & MS_KERNMOUNT)) {
+                struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+                /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
+                 * over the ipc namespace.
+                 */
+                if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+                        return ERR_PTR(-EPERM);
+
+                data = ns;
+        }
         return mount_ns(fs_type, flags, data, mqueue_fill_super);
 }
 
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index c1c3dc1c6023..bea15bdf82b0 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -181,6 +181,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
         int nr;
         int rc;
         struct task_struct *task, *me = current;
+        int init_pids = thread_group_leader(me) ? 1 : 2;
 
         /* Don't allow any more processes into the pid namespace */
         disable_pid_allocation(pid_ns);
@@ -230,7 +231,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
          */
         for (;;) {
                 set_current_state(TASK_UNINTERRUPTIBLE);
-                if (pid_ns->nr_hashed == 1)
+                if (pid_ns->nr_hashed == init_pids)
                         break;
                 schedule();
         }
diff --git a/kernel/user.c b/kernel/user.c
index e81978e8c03b..8e635a18ab52 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -51,6 +51,8 @@ struct user_namespace init_user_ns = {
         .owner = GLOBAL_ROOT_UID,
         .group = GLOBAL_ROOT_GID,
         .proc_inum = PROC_USER_INIT_INO,
+        .may_mount_sysfs = true,
+        .may_mount_proc = true,
 };
 EXPORT_SYMBOL_GPL(init_user_ns);
 
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index b14f4d342043..a54f26f82eb2 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -61,6 +61,15 @@ int create_user_ns(struct cred *new)
         kgid_t group = new->egid;
         int ret;
 
+        /*
+         * Verify that we can not violate the policy of which files
+         * may be accessed that is specified by the root directory,
+         * by verifing that the root directory is at the root of the
+         * mount namespace which allows all files to be accessed.
+         */
+        if (current_chrooted())
+                return -EPERM;
+
         /* The creator needs a mapping in the parent user namespace
          * or else we won't be able to reasonably tell userspace who
          * created a user_namespace.
@@ -87,6 +96,8 @@ int create_user_ns(struct cred *new)
 
         set_cred_user_ns(new, ns);
 
+        update_mnt_policy(ns);
+
         return 0;
 }
 
diff --git a/net/core/scm.c b/net/core/scm.c
index 905dcc6ad1e3..2dc6cdaaae8a 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -24,6 +24,7 @@
 #include <linux/interrupt.h>
 #include <linux/netdevice.h>
 #include <linux/security.h>
+#include <linux/pid_namespace.h>
 #include <linux/pid.h>
 #include <linux/nsproxy.h>
 #include <linux/slab.h>
@@ -52,7 +53,8 @@ static __inline__ int scm_check_creds(struct ucred *creds)
         if (!uid_valid(uid) || !gid_valid(gid))
                 return -EINVAL;
 
-        if ((creds->pid == task_tgid_vnr(current) || nsown_capable(CAP_SYS_ADMIN)) &&
+        if ((creds->pid == task_tgid_vnr(current) ||
+             ns_capable(current->nsproxy->pid_ns->user_ns, CAP_SYS_ADMIN)) &&
             ((uid_eq(uid, cred->uid)   || uid_eq(uid, cred->euid) ||
               uid_eq(uid, cred->suid)) || nsown_capable(CAP_SETUID)) &&
             ((gid_eq(gid, cred->gid)   || gid_eq(gid, cred->egid) ||
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 23414b93771f..13c88fbcf037 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -347,10 +347,8 @@ int yama_ptrace_traceme(struct task_struct *parent)
         /* Only disallow PTRACE_TRACEME on more aggressive settings. */
         switch (ptrace_scope) {
         case YAMA_SCOPE_CAPABILITY:
-                rcu_read_lock();
-                if (!ns_capable(__task_cred(parent)->user_ns, CAP_SYS_PTRACE))
+                if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE))
                         rc = -EPERM;
-                rcu_read_unlock();
                 break;
         case YAMA_SCOPE_NO_ATTACH:
                 rc = -EPERM;