[PATCH review 0/12] General unprivileged mount support v2

@@ -434,7 +434,7 @@ static int mdc_unpack_acl(struct ptlrpc_request *req, struct lustre_md *md)
 		return rc;
 	}
 
-	rc = posix_acl_valid(acl);
+	rc = posix_acl_valid(&init_user_ns, acl);
 	if (rc) {
 		CERROR("validate acl: %d\n", rc);
 		posix_acl_release(acl);

@@ -266,7 +266,7 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
 		if (IS_ERR(acl))
 			return PTR_ERR(acl);
 		else if (acl) {
-			retval = posix_acl_valid(acl);
+			retval = posix_acl_valid(inode->i_sb->s_user_ns, acl);
 			if (retval)
 				goto err_out;
 		}

@@ -205,7 +205,7 @@ posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
  */
 int
-posix_acl_valid(const struct posix_acl *acl)
+posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
 {
 	const struct posix_acl_entry *pa, *pe;
 	int state = ACL_USER_OBJ;

@@ -225,7 +225,7 @@ posix_acl_valid(const struct posix_acl *acl)
 			case ACL_USER:
 				if (state != ACL_USER)
 					return -EINVAL;
-				if (!uid_valid(pa->e_uid))
+				if (!kuid_has_mapping(user_ns, pa->e_uid))
 					return -EINVAL;
 				needs_mask = 1;
 				break;

@@ -240,7 +240,7 @@ posix_acl_valid(const struct posix_acl *acl)
 			case ACL_GROUP:
 				if (state != ACL_GROUP)
 					return -EINVAL;
-				if (!gid_valid(pa->e_gid))
+				if (!kgid_has_mapping(user_ns, pa->e_gid))
 					return -EINVAL;
 				needs_mask = 1;
 				break;

@@ -845,7 +845,7 @@ posix_acl_xattr_set(const struct xattr_handler *handler,
 			return PTR_ERR(acl);
 
 		if (acl) {
-			ret = posix_acl_valid(acl);
+			ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
 			if (ret)
 				goto out;
 		}

@@ -81,7 +81,7 @@ posix_acl_release(struct posix_acl *acl)
 
 extern void posix_acl_init(struct posix_acl *, int);
 extern struct posix_acl *posix_acl_alloc(int, gfp_t);
-extern int posix_acl_valid(const struct posix_acl *);
+extern int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
 extern int posix_acl_permission(struct inode *, const struct posix_acl *, int);
 extern struct posix_acl *posix_acl_from_mode(umode_t, gfp_t);
 extern int posix_acl_equiv_mode(const struct posix_acl *, umode_t *);

@@ -177,12 +177,12 @@ static inline gid_t from_kgid_munged(struct user_namespace *to, kgid_t kgid)
 
 static inline bool kuid_has_mapping(struct user_namespace *ns, kuid_t uid)
 {
-	return true;
+	return uid_valid(uid);
 }
 
 static inline bool kgid_has_mapping(struct user_namespace *ns, kgid_t gid)
 {
-	return true;
+	return gid_valid(gid);
 }
 
 #endif /* CONFIG_USER_NS */

@@ -255,6 +255,17 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de
 	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
 		return 0;
 
+	/*
+	 * Verify that uid/gid changes are valid in the target
+	 * namespace of the superblock.
+	 */
+	if (ia_valid & ATTR_UID &&
+	    !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
+		return -EOVERFLOW;
+	if (ia_valid & ATTR_GID &&
+	    !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
+		return -EOVERFLOW;
+
 	error = security_inode_setattr(dentry, attr);
 	if (error)
 		return error;

@@ -901,6 +901,7 @@ static inline int may_follow_link(struct nameidata *nd)
 {
 	const struct inode *inode;
 	const struct inode *parent;
+	kuid_t puid;
 
 	if (!sysctl_protected_symlinks)
 		return 0;

@@ -916,7 +917,8 @@ static inline int may_follow_link(struct nameidata *nd)
 		return 0;
 
 	/* Allowed if parent directory and link owner match. */
-	if (uid_eq(parent->i_uid, inode->i_uid))
+	puid = parent->i_uid;
+	if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
 		return 0;
 
 	if (nd->flags & LOOKUP_RCU)

@@ -689,6 +689,8 @@ EXPORT_SYMBOL(set_security_override_from_ctx);
  */
 int set_create_files_as(struct cred *new, struct inode *inode)
 {
+	if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
+		return -EINVAL;
 	new->fsuid = inode->i_uid;
 	new->fsgid = inode->i_gid;
 	return security_kernel_create_files_as(new, inode);

@@ -266,6 +266,14 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de
 	    !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
 		return -EOVERFLOW;
 
+	/* Don't allow modifications of files with invalid uids or
+	 * gids unless those uids & gids are being made valid.
+	 */
+	if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
+		return -EOVERFLOW;
+	if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
+		return -EOVERFLOW;
+
 	error = security_inode_setattr(dentry, attr);
 	if (error)
 		return error;

@@ -1617,6 +1617,13 @@ bool atime_needs_update(const struct path *path, struct inode *inode)
 
 	if (inode->i_flags & S_NOATIME)
 		return false;
+
+	/* Atime updates will likely cause i_uid and i_gid to be written
+	 * back improprely if their true value is unknown to the vfs.
+	 */
+	if (HAS_UNMAPPED_ID(inode))
+		return false;
+
 	if (IS_NOATIME(inode))
 		return false;
 	if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode))

@@ -410,6 +410,14 @@ int __inode_permission(struct inode *inode, int mask)
 		 */
 		if (IS_IMMUTABLE(inode))
 			return -EACCES;
+
+		/*
+		 * Updating mtime will likely cause i_uid and i_gid to be
+		 * written back improperly if their true value is unknown
+		 * to the vfs.
+		 */
+		if (HAS_UNMAPPED_ID(inode))
+			return -EACCES;
 	}
 
 	retval = do_inode_permission(inode, mask);

@@ -2759,10 +2767,11 @@ EXPORT_SYMBOL(__check_sticky);
  *	c. have CAP_FOWNER capability
  *  6. If the victim is append-only or immutable we can't do antyhing with
  *     links pointing to it.
- *  7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
- *  8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
- *  9. We can't remove a root or mountpoint.
- * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
+ *  7. If the victim has an unknown uid or gid we can't change the inode.
+ *  8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
+ *  9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
+ * 10. We can't remove a root or mountpoint.
+ * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
  *     nfs_async_unlink().
  */
 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)

@@ -2784,7 +2793,7 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
 		return -EPERM;
 
 	if (check_sticky(dir, inode) || IS_APPEND(inode) ||
-	    IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
+	    IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
 		return -EPERM;
 	if (isdir) {
 		if (!d_is_dir(victim))

@@ -4190,6 +4199,13 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
 	 */
 	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
 		return -EPERM;
+	/*
+	 * Updating the link count will likely cause i_uid and i_gid to
+	 * be writen back improperly if their true value is unknown to
+	 * the vfs.
+	 */
+	if (HAS_UNMAPPED_ID(inode))
+		return -EPERM;
 	if (!dir->i_op->link)
 		return -EPERM;
 	if (S_ISDIR(inode->i_mode))

@@ -38,6 +38,13 @@ xattr_permission(struct inode *inode, const char *name, int mask)
 	if (mask & MAY_WRITE) {
 		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 			return -EPERM;
+		/*
+		 * Updating an xattr will likely cause i_uid and i_gid
+		 * to be writen back improperly if their true value is
+		 * unknown to the vfs.
+		 */
+		if (HAS_UNMAPPED_ID(inode))
+			return -EPERM;
 	}
 
 	/*

@@ -1874,6 +1874,11 @@ struct super_operations {
 #define IS_WHITEOUT(inode)	(S_ISCHR(inode->i_mode) && \
 				 (inode)->i_rdev == WHITEOUT_DEV)
 
+static inline bool HAS_UNMAPPED_ID(struct inode *inode)
+{
+	return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid);
+}
+
 /*
  * Inode state bits.  Protected by inode->i_lock
  *

@@ -2814,16 +2814,22 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
  *  1. We can't do it if child already exists (open has special treatment for
  *     this case, but since we are inlined it's OK)
  *  2. We can't do it if dir is read-only (done in permission())
- *  3. We should have write and exec permissions on dir
- *  4. We can't do it if dir is immutable (done in permission())
+ *  3. We can't do it if the fs can't represent the fsuid or fsgid.
+ *  4. We should have write and exec permissions on dir
+ *  5. We can't do it if dir is immutable (done in permission())
  */
 static inline int may_create(struct inode *dir, struct dentry *child)
 {
+	struct user_namespace *s_user_ns;
 	audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
 	if (child->d_inode)
 		return -EEXIST;
 	if (IS_DEADDIR(dir))
 		return -ENOENT;
+	s_user_ns = dir->i_sb->s_user_ns;
+	if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
+	    !kgid_has_mapping(s_user_ns, current_fsgid()))
+		return -EOVERFLOW;
 	return inode_permission(dir, MAY_WRITE | MAY_EXEC);
 }
 

@@ -841,6 +841,9 @@ struct dquot *dqget(struct super_block *sb, struct kqid qid)
 	unsigned int hashent = hashfn(sb, qid);
 	struct dquot *dquot, *empty = NULL;
 
+	if (!qid_has_mapping(sb->s_user_ns, qid))
+		return ERR_PTR(-EINVAL);
+
         if (!sb_has_quota_active(sb, qid.type))
 		return ERR_PTR(-ESRCH);
 we_slept:

@@ -211,7 +211,7 @@ static int quota_getquota(struct super_block *sb, int type, qid_t id,
 	if (!sb->s_qcop->get_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_dqblk(sb, qid, &fdq);
 	if (ret)

@@ -237,7 +237,7 @@ static int quota_getnextquota(struct super_block *sb, int type, qid_t id,
 	if (!sb->s_qcop->get_nextdqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_nextdqblk(sb, &qid, &fdq);
 	if (ret)

@@ -288,7 +288,7 @@ static int quota_setquota(struct super_block *sb, int type, qid_t id,
 	if (!sb->s_qcop->set_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	copy_from_if_dqblk(&fdq, &idq);
 	return sb->s_qcop->set_dqblk(sb, qid, &fdq);

@@ -581,7 +581,7 @@ static int quota_setxquota(struct super_block *sb, int type, qid_t id,
 	if (!sb->s_qcop->set_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	/* Are we actually setting timer / warning limits for all users? */
 	if (from_kqid(&init_user_ns, qid) == 0 &&

@@ -642,7 +642,7 @@ static int quota_getxquota(struct super_block *sb, int type, qid_t id,
 	if (!sb->s_qcop->get_dqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_dqblk(sb, qid, &qdq);
 	if (ret)

@@ -669,7 +669,7 @@ static int quota_getnextxquota(struct super_block *sb, int type, qid_t id,
 	if (!sb->s_qcop->get_nextdqblk)
 		return -ENOSYS;
 	qid = make_kqid(current_user_ns(), type, id);
-	if (!qid_valid(qid))
+	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	ret = sb->s_qcop->get_nextdqblk(sb, &qid, &qdq);
 	if (ret)

@@ -179,6 +179,16 @@ static inline struct kqid make_kqid_projid(kprojid_t projid)
 	return kqid;
 }
 
+/**
+ *	qid_has_mapping - Report if a qid maps into a user namespace.
+ *	@ns:  The user namespace to see if a value maps into.
+ *	@qid: The kernel internal quota identifier to test.
+ */
+static inline bool qid_has_mapping(struct user_namespace *ns, struct kqid qid)
+{
+	return from_kqid(ns, qid) != (qid_t) -1;
+}
+
 
 extern spinlock_t dq_data_lock;
 

@@ -584,7 +584,7 @@ static int quota_setxquota(struct super_block *sb, int type, qid_t id,
 	if (!qid_has_mapping(sb->s_user_ns, qid))
 		return -EINVAL;
 	/* Are we actually setting timer / warning limits for all users? */
-	if (from_kqid(&init_user_ns, qid) == 0 &&
+	if (from_kqid(sb->s_user_ns, qid) == 0 &&
 	    fdq.d_fieldmask & (FS_DQ_WARNS_MASK | FS_DQ_TIMER_MASK)) {
 		struct qc_info qinfo;
 		int ret;

@@ -2271,6 +2271,11 @@ static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
 		error = -EINVAL;
 		goto out_fmt;
 	}
+	/* Filesystems outside of init_user_ns not yet supported */
+	if (sb->s_user_ns != &init_user_ns) {
+		error = -EINVAL;
+		goto out_fmt;
+	}
 	/* Usage always has to be set... */
 	if (!(flags & DQUOT_USAGE_ENABLED)) {
 		error = -EINVAL;

@@ -151,8 +151,8 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
 	memset(&hmac_misc, 0, sizeof(hmac_misc));
 	hmac_misc.ino = inode->i_ino;
 	hmac_misc.generation = inode->i_generation;
-	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
-	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
+	hmac_misc.uid = from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
+	hmac_misc.gid = from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
 	hmac_misc.mode = inode->i_mode;
 	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
 	if (evm_hmac_attrs & EVM_ATTR_FSUUID)

@@ -831,31 +831,6 @@ static inline void i_size_write(struct inode *inode, loff_t i_size)
 #endif
 }
 
-/* Helper functions so that in most cases filesystems will
- * not need to deal directly with kuid_t and kgid_t and can
- * instead deal with the raw numeric values that are stored
- * in the filesystem.
- */
-static inline uid_t i_uid_read(const struct inode *inode)
-{
-	return from_kuid(&init_user_ns, inode->i_uid);
-}
-
-static inline gid_t i_gid_read(const struct inode *inode)
-{
-	return from_kgid(&init_user_ns, inode->i_gid);
-}
-
-static inline void i_uid_write(struct inode *inode, uid_t uid)
-{
-	inode->i_uid = make_kuid(&init_user_ns, uid);
-}
-
-static inline void i_gid_write(struct inode *inode, gid_t gid)
-{
-	inode->i_gid = make_kgid(&init_user_ns, gid);
-}
-
 static inline unsigned iminor(const struct inode *inode)
 {
 	return MINOR(inode->i_rdev);

@@ -1461,6 +1436,31 @@ struct super_block {
 	struct list_head	s_inodes;	/* all inodes */
 };
 
+/* Helper functions so that in most cases filesystems will
+ * not need to deal directly with kuid_t and kgid_t and can
+ * instead deal with the raw numeric values that are stored
+ * in the filesystem.
+ */
+static inline uid_t i_uid_read(const struct inode *inode)
+{
+	return from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
+}
+
+static inline gid_t i_gid_read(const struct inode *inode)
+{
+	return from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
+}
+
+static inline void i_uid_write(struct inode *inode, uid_t uid)
+{
+	inode->i_uid = make_kuid(inode->i_sb->s_user_ns, uid);
+}
+
+static inline void i_gid_write(struct inode *inode, gid_t gid)
+{
+	inode->i_gid = make_kgid(inode->i_sb->s_user_ns, gid);
+}
+
 extern struct timespec current_fs_time(struct super_block *sb);
 
 /*