Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754126AbdGYTnM (ORCPT ); Tue, 25 Jul 2017 15:43:12 -0400 Received: from h2.hallyn.com ([78.46.35.8]:58382 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754057AbdGYTnJ (ORCPT ); Tue, 25 Jul 2017 15:43:09 -0400 Date: Tue, 25 Jul 2017 14:43:15 -0500 From: "Serge E. Hallyn" To: Mehmet Kayaalp Cc: ima-devel , containers , linux-kernel , linux-security-module , Tycho Andersen , "Serge E . Hallyn" , Yuqiong Sun , David Safford , Mehmet Kayaalp , Stefan Berger Subject: Re: [RFC PATCH 2/5] ima: Add ns_status for storing namespaced iint data Message-ID: <20170725194315.GA2397@mail.hallyn.com> References: <20170720225033.21298-1-mkayaalp@linux.vnet.ibm.com> <20170720225033.21298-3-mkayaalp@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170720225033.21298-3-mkayaalp@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3322 Lines: 121 ... > +static void free_ns_status_cache(struct ima_namespace *ns) > +{ > + struct ns_status *status, *next; > + > + write_lock(&ns->ns_status_lock); > + rbtree_postorder_for_each_entry_safe(status, next, > + &ns->ns_status_tree, rb_node) > + kmem_cache_free(ns->ns_status_cache, status); > + ns->ns_status_tree = RB_ROOT; > + write_unlock(&ns->ns_status_lock); > + kmem_cache_destroy(ns->ns_status_cache); > +} > + > static void destroy_ima_ns(struct ima_namespace *ns) > { > put_user_ns(ns->user_ns); > ns_free_inum(&ns->ns); > + free_ns_status_cache(ns); > kfree(ns); > } > > @@ -181,3 +198,106 @@ struct ima_namespace init_ima_ns = { > .parent = NULL, > }; > EXPORT_SYMBOL(init_ima_ns); > + > +/* > + * __ima_ns_status_find - return the ns_status associated with an inode > + */ > +static struct ns_status *__ima_ns_status_find(struct ima_namespace *ns, > + struct inode *inode) > +{ > + struct ns_status *status; > + struct rb_node *n = ns->ns_status_tree.rb_node; > + > + while (n) { > + status = rb_entry(n, struct ns_status, rb_node); > + > + if (inode < status->inode) > + n = n->rb_left; > + else if (inode->i_ino > status->i_ino) > + n = n->rb_right; > + else > + break; > + } > + if (!n) > + return NULL; > + > + return status; > +} > + > +/* > + * ima_ns_status_find - return the ns_status associated with an inode > + */ > +static struct ns_status *ima_ns_status_find(struct ima_namespace *ns, > + struct inode *inode) > +{ > + struct ns_status *status; > + > + read_lock(&ns->ns_status_lock); > + status = __ima_ns_status_find(ns, inode); > + read_unlock(&ns->ns_status_lock); > + > + return status; > +} ... > + > +struct ns_status *ima_get_ns_status(struct ima_namespace *ns, > + struct inode *inode) > +{ > + struct ns_status *status; > + int skip_insert = 0; > + > + status = ima_ns_status_find(ns, inode); > + if (status) { > + /* > + * Unlike integrity_iint_cache we are not free'ing the > + * ns_status data when the inode is free'd. So, in addition to > + * checking the inode pointer, we need to make sure the > + * (i_generation, i_ino) pair matches as well. In the future > + * we might want to add support for lazily walking the rbtree > + * to clean it up. > + */ > + if (inode->i_ino == status->i_ino && > + inode->i_generation == status->i_generation) > + return status; > + > + /* Same inode number is reused, overwrite the ns_status */ > + skip_insert = 1; > + } else { > + status = kmem_cache_alloc(ns->ns_status_cache, GFP_NOFS); > + if (!status) > + return ERR_PTR(-ENOMEM); > + } What prevents the status from being freed between the read_lock in ima_ns_status_find() and the write_lock in the following line? IIUC it's that ns is always current's ima_ns, which will pin the ns and cause no statuses to be freed. But then the ns should probably not be passed in here? Or a comment should say that ns must be pinned? Just trying to make sure I understand the locking. > + write_lock(&ns->ns_status_lock); > + > + if (!skip_insert) > + insert_ns_status(ns, inode, status); > + > + status->inode = inode; > + status->i_ino = inode->i_ino; > + status->i_generation = inode->i_generation; > + status->flags = 0UL; > + write_unlock(&ns->ns_status_lock); > + > + return status; > +} > -- > 2.9.4