1 files changed, 52 insertions, 14 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 2b042c42fbc4..b14f4d342043 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -21,6 +21,7 @@
 #include <linux/uaccess.h>
 #include <linux/ctype.h>
 #include <linux/projid.h>
+#include <linux/fs_struct.h>
 
 static struct kmem_cache *user_ns_cachep __read_mostly;
 
@@ -78,7 +79,7 @@ int create_user_ns(struct cred *new)
                 return ret;
         }
 
-        kref_init(&ns->kref);
+        atomic_set(&ns->count, 1);
         /* Leave the new->user_ns reference with the new user namespace. */
         ns->parent = parent_ns;
         ns->owner = owner;
@@ -104,15 +105,16 @@ int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
         return create_user_ns(cred);
 }
 
-void free_user_ns(struct kref *kref)
+void free_user_ns(struct user_namespace *ns)
 {
-        struct user_namespace *parent, *ns =
-                container_of(kref, struct user_namespace, kref);
+        struct user_namespace *parent;
 
-        parent = ns->parent;
-        proc_free_inum(ns->proc_inum);
-        kmem_cache_free(user_ns_cachep, ns);
-        put_user_ns(parent);
+        do {
+                parent = ns->parent;
+                proc_free_inum(ns->proc_inum);
+                kmem_cache_free(user_ns_cachep, ns);
+                ns = parent;
+        } while (atomic_dec_and_test(&parent->count));
 }
 EXPORT_SYMBOL(free_user_ns);
 
@@ -519,6 +521,42 @@ struct seq_operations proc_projid_seq_operations = {
         .show = projid_m_show,
 };
 
+static bool mappings_overlap(struct uid_gid_map *new_map, struct uid_gid_extent *extent)
+{
+        u32 upper_first, lower_first, upper_last, lower_last;
+        unsigned idx;
+
+        upper_first = extent->first;
+        lower_first = extent->lower_first;
+        upper_last = upper_first + extent->count - 1;
+        lower_last = lower_first + extent->count - 1;
+
+        for (idx = 0; idx < new_map->nr_extents; idx++) {
+                u32 prev_upper_first, prev_lower_first;
+                u32 prev_upper_last, prev_lower_last;
+                struct uid_gid_extent *prev;
+
+                prev = &new_map->extent[idx];
+
+                prev_upper_first = prev->first;
+                prev_lower_first = prev->lower_first;
+                prev_upper_last = prev_upper_first + prev->count - 1;
+                prev_lower_last = prev_lower_first + prev->count - 1;
+
+                /* Does the upper range intersect a previous extent? */
+                if ((prev_upper_first <= upper_last) &&
+                    (prev_upper_last >= upper_first))
+                        return true;
+
+                /* Does the lower range intersect a previous extent? */
+                if ((prev_lower_first <= lower_last) &&
+                    (prev_lower_last >= lower_first))
+                        return true;
+        }
+        return false;
+}
+
+
 static DEFINE_MUTEX(id_map_mutex);
 
 static ssize_t map_write(struct file *file, const char __user *buf,
@@ -531,7 +569,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
         struct user_namespace *ns = seq->private;
         struct uid_gid_map new_map;
         unsigned idx;
-        struct uid_gid_extent *extent, *last = NULL;
+        struct uid_gid_extent *extent = NULL;
         unsigned long page = 0;
         char *kbuf, *pos, *next_line;
         ssize_t ret = -EINVAL;
@@ -634,14 +672,11 @@ static ssize_t map_write(struct file *file, const char __user *buf,
                 if ((extent->lower_first + extent->count) <= extent->lower_first)
                         goto out;
 
-                /* For now only accept extents that are strictly in order */
-                if (last &&
-                    (((last->first + last->count) > extent->first) ||
-                     ((last->lower_first + last->count) > extent->lower_first)))
+                /* Do the ranges in extent overlap any previous extents? */
+                if (mappings_overlap(&new_map, extent))
                         goto out;
 
                 new_map.nr_extents++;
-                last = extent;
 
                 /* Fail if the file contains too many extents */
                 if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
@@ -803,6 +838,9 @@ static int userns_install(struct nsproxy *nsproxy, void *ns)
         if (atomic_read(&current->mm->mm_users) > 1)
                 return -EINVAL;
 
+        if (current->fs->users != 1)
+                return -EINVAL;
+
         if (!ns_capable(user_ns, CAP_SYS_ADMIN))
                 return -EPERM;