5 files changed, 28 insertions, 23 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 9f4f5fecc096..f0c4ace408e4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1732,11 +1732,9 @@ EXPORT_SYMBOL(inode_init_owner);
  */
 bool inode_owner_or_capable(const struct inode *inode)
 {
-        struct user_namespace *ns = inode_userns(inode);
-
-        if (current_user_ns() == ns && current_fsuid() == inode->i_uid)
+        if (current_fsuid() == inode->i_uid)
                 return true;
-        if (ns_capable(ns, CAP_FOWNER))
+        if (inode_capable(inode, CAP_FOWNER))
                 return true;
         return false;
 }
diff --git a/fs/namei.c b/fs/namei.c
index 701954d68ac7..941c4362e298 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -228,9 +228,6 @@ static int acl_permission_check(struct inode *inode, int mask)
 {
         unsigned int mode = inode->i_mode;
 
-        if (current_user_ns() != inode_userns(inode))
-                goto other_perms;
-
         if (likely(current_fsuid() == inode->i_uid))
                 mode >>= 6;
         else {
@@ -244,7 +241,6 @@ static int acl_permission_check(struct inode *inode, int mask)
                         mode >>= 3;
         }
 
-other_perms:
         /*
          * If the DACs are ok we don't need any capability check.
          */
@@ -280,10 +276,10 @@ int generic_permission(struct inode *inode, int mask)
 
         if (S_ISDIR(inode->i_mode)) {
                 /* DACs are overridable for directories */
-                if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
+                if (inode_capable(inode, CAP_DAC_OVERRIDE))
                         return 0;
                 if (!(mask & MAY_WRITE))
-                        if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
+                        if (inode_capable(inode, CAP_DAC_READ_SEARCH))
                                 return 0;
                 return -EACCES;
         }
@@ -293,7 +289,7 @@ int generic_permission(struct inode *inode, int mask)
          * at least one exec bit set.
          */
         if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
-                if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
+                if (inode_capable(inode, CAP_DAC_OVERRIDE))
                         return 0;
 
         /*
@@ -301,7 +297,7 @@ int generic_permission(struct inode *inode, int mask)
          */
         mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
         if (mask == MAY_READ)
-                if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
+                if (inode_capable(inode, CAP_DAC_READ_SEARCH))
                         return 0;
 
         return -EACCES;
@@ -1964,15 +1960,11 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)
 
         if (!(dir->i_mode & S_ISVTX))
                 return 0;
-        if (current_user_ns() != inode_userns(inode))
-                goto other_userns;
         if (inode->i_uid == fsuid)
                 return 0;
         if (dir->i_uid == fsuid)
                 return 0;
-
-other_userns:
-        return !ns_capable(inode_userns(inode), CAP_FOWNER);
+        return !inode_capable(inode, CAP_FOWNER);
 }
 
 /*
diff --git a/include/linux/capability.h b/include/linux/capability.h
index 12d52dedb229..a76eca907470 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -374,6 +374,7 @@ struct cpu_vfs_cap_data {
 
 #ifdef __KERNEL__
 
+struct inode;
 struct dentry;
 struct user_namespace;
 
@@ -548,6 +549,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
 extern bool capable(int cap);
 extern bool ns_capable(struct user_namespace *ns, int cap);
 extern bool nsown_capable(int cap);
+extern bool inode_capable(const struct inode *inode, int cap);
 
 /* audit system wants to get cap info from files as well */
 extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 135693e79f2b..a6c5efbee0d7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1522,12 +1522,6 @@ enum {
 #define vfs_check_frozen(sb, level) \
         wait_event((sb)->s_wait_unfrozen, ((sb)->s_frozen < (level)))
 
-/*
- * until VFS tracks user namespaces for inodes, just make all files
- * belong to init_user_ns
- */
-extern struct user_namespace init_user_ns;
-#define inode_userns(inode) (&init_user_ns)
 extern bool inode_owner_or_capable(const struct inode *inode);
 
 /* not quite ready to be deprecated, but... */
diff --git a/kernel/capability.c b/kernel/capability.c
index 3f1adb6c6470..cc5f0718215d 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -419,3 +419,22 @@ bool nsown_capable(int cap)
 {
         return ns_capable(current_user_ns(), cap);
 }
+
+/**
+ * inode_capable - Check superior capability over inode
+ * @inode: The inode in question
+ * @cap: The capability in question
+ *
+ * Return true if the current task has the given superior capability
+ * targeted at it's own user namespace and that the given inode is owned
+ * by the current user namespace or a child namespace.
+ *
+ * Currently inodes can only be owned by the initial user namespace.
+ *
+ */
+bool inode_capable(const struct inode *inode, int cap)
+{
+        struct user_namespace *ns = current_user_ns();
+
+        return ns_capable(ns, cap) && (ns == &init_user_ns);
+}