From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755009Ab3LCOyA (ORCPT ); Tue, 3 Dec 2013 09:54:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48493 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753482Ab3LCOxZ (ORCPT ); Tue, 3 Dec 2013 09:53:25 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH4/5] KEYS: Fix searching of nested keyrings From: David Howells To: torvalds@linux-foundation.org, jmorris@namei.org Cc: Stephen Gallagher , keyrings@linux-nfs.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 03 Dec 2013 14:53:20 +0000 Message-ID: <20131203145320.30689.27703.stgit@warthog.procyon.org.uk> In-Reply-To: <20131203145250.30689.28039.stgit@warthog.procyon.org.uk> References: <20131203145250.30689.28039.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a keyring contains more than 16 keyrings (the capacity of a single node in the associative array) then those keyrings are split over multiple nodes arranged as a tree. If search_nested_keyrings() is called to search the keyring then it will attempt to manually walk over just the 0 branch of the associative array tree where all the keyring links are stored. This works provided the key is found before the algorithm steps from one node containing keyrings to a child node or if there are sufficiently few keyring links that the keyrings are all in one node. However, if the algorithm does need to step from a node to a child node, it doesn't change the node pointer unless a shortcut also gets transited. This means that the algorithm will keep scanning the same node over and over again without terminating and without returning. To fix this, move the internal-pointer-to-node translation from inside the shortcut transit handler so that it applies it to node arrival as well. This can be tested by: r=`keyctl newring sandbox @s` for ((i=0; i<=16; i++)); do keyctl newring ring$i $r; done for ((i=0; i<=16; i++)); do keyctl add user a$i a %:ring$i; done for ((i=0; i<=16; i++)); do keyctl search $r user a$i; done for ((i=17; i<=20; i++)); do keyctl search $r user a$i; done The searches should all complete successfully (or with an error for 17-20), but instead one or more of them will hang. Signed-off-by: David Howells Tested-by: Stephen Gallagher --- security/keys/keyring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 3dd8445cd489..d46cbc5e335e 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -690,8 +690,8 @@ descend_to_node: smp_read_barrier_depends(); ptr = ACCESS_ONCE(shortcut->next_node); BUG_ON(!assoc_array_ptr_is_node(ptr)); - node = assoc_array_ptr_to_node(ptr); } + node = assoc_array_ptr_to_node(ptr); begin_node: kdebug("begin_node");