From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753291AbdEJUtI (ORCPT ); Wed, 10 May 2017 16:49:08 -0400 Received: from smtp-sh2.infomaniak.ch ([128.65.195.6]:38978 "EHLO smtp-sh2.infomaniak.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751096AbdEJUtG (ORCPT ); Wed, 10 May 2017 16:49:06 -0400 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Casey Schaufler , James Morris , Kees Cook , "Serge E . Hallyn" , Tetsuo Handa , linux-security-module@vger.kernel.org Subject: [PATCH v3] LSM: Enable multiple calls to security_add_hooks() for the same LSM Date: Wed, 10 May 2017 22:48:48 +0200 Message-Id: <20170510204848.1555-1-mic@digikod.net> X-Mailer: git-send-email 2.11.0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Antivirus: Dr.Web (R) for Unix mail servers drweb plugin ver.6.0.2.8 X-Antivirus-Code: 0x100000 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The commit d69dece5f5b6 ("LSM: Add /sys/kernel/security/lsm") extend security_add_hooks() with a new parameter to register the LSM name, which may be useful to make the list of currently loaded LSM available to userspace. However, there is no clean way for an LSM to split its hook declarations into multiple files, which may reduce the mess with all the included files (needed for LSM hook argument types) and make the source code easier to review and maintain. This change allows an LSM to register multiple times its hook while keeping a consistent list of LSM names as described in Documentation/security/LSM.txt . The list reflects the order in which checks are made. This patch only check for the last registered LSM. If an LSM register multiple times its hooks, interleaved with other LSM registrations (which should not happen), its name will still appear in the same order that the hooks are called, hence multiple times. To sum up, "capability,selinux,foo,foo" will be replaced with "capability,selinux,foo", however "capability,foo,selinux,foo" will remain as is. Signed-off-by: Mickaël Salaün Cc: Casey Schaufler Cc: James Morris Cc: Kees Cook Cc: Serge E. Hallyn Cc: Tetsuo Handa Link: https://lkml.kernel.org/r/ccad825b-7a58-e499-e51b-bd7c98581afe@schaufler-ca.com --- security/security.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/security/security.c b/security/security.c index 549bddcc2116..54b1e395978a 100644 --- a/security/security.c +++ b/security/security.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #define MAX_LSM_EVM_XATTR 2 @@ -86,6 +87,21 @@ static int __init choose_lsm(char *str) } __setup("security=", choose_lsm); +static bool match_last_lsm(const char *list, const char *lsm) +{ + const char *last; + + if (WARN_ON(!list || !lsm)) + return false; + last = strrchr(list, ','); + if (last) + /* Pass the comma, strcmp() will check for '\0' */ + last++; + else + last = list; + return !strcmp(last, lsm); +} + static int lsm_append(char *new, char **result) { char *cp; @@ -93,6 +109,9 @@ static int lsm_append(char *new, char **result) if (*result == NULL) { *result = kstrdup(new, GFP_KERNEL); } else { + /* Check if it is the last registered name */ + if (match_last_lsm(*result, new)) + return 0; cp = kasprintf(GFP_KERNEL, "%s,%s", *result, new); if (cp == NULL) return -ENOMEM; -- 2.11.0