From patchwork Fri Jan 17 02:18:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lakshmi Ramasubramanian X-Patchwork-Id: 11338161 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 867421820 for ; Fri, 17 Jan 2020 02:18:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62B7F20748 for ; Fri, 17 Jan 2020 02:18:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="S27CgPjr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732223AbgAQCS0 (ORCPT ); Thu, 16 Jan 2020 21:18:26 -0500 Received: from linux.microsoft.com ([13.77.154.182]:54188 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731794AbgAQCS0 (ORCPT ); Thu, 16 Jan 2020 21:18:26 -0500 Received: from nramas-ThinkStation-P520.corp.microsoft.com (unknown [131.107.174.108]) by linux.microsoft.com (Postfix) with ESMTPSA id 2B2B620B4798; Thu, 16 Jan 2020 18:18:25 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 2B2B620B4798 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1579227505; bh=3DPtxdzEuRBvzO+EeSGb0wH3lYD0uB0b2KEtfivyzHM=; h=From:To:Cc:Subject:Date:From; b=S27CgPjrSEEqIgHkbbHLBRnOjwZi0eK/hWi0J3rauKmjDqE0IIaMBThHyMWVye+DL 0E6aWpJcRIrUZgKrwxl3TePi6oDFRZsSlg01FH7UN28Nr/94Nru0byFqDv0GWtsJul J2z7szb+pz0qE0MVqSmGGQvFlzKyB1myO10rwEVI= From: Lakshmi Ramasubramanian To: zohar@linux.ibm.com, linux-integrity@vger.kernel.org Cc: sashal@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] IMA: pre-allocate buffer to hold keyrings string Date: Thu, 16 Jan 2020 18:18:21 -0800 Message-Id: <20200117021821.2566-1-nramas@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org ima_match_keyring() is called while holding rcu read lock. Since this function executes in atomic context, it should not call any function that can sleep (such as kstrdup()). This patch pre-allocates a buffer to hold the keyrings string read from the IMA policy and uses that to match the given keyring. Signed-off-by: Lakshmi Ramasubramanian Fixes: e9085e0ad38a ("IMA: Add support to limit measuring keys") --- security/integrity/ima/ima_policy.c | 38 +++++++++++++++++++++++------ 1 file changed, 30 insertions(+), 8 deletions(-) diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 9963863d6c92..3e296051feea 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -208,6 +208,10 @@ static LIST_HEAD(ima_policy_rules); static LIST_HEAD(ima_temp_rules); static struct list_head *ima_rules; +/* Pre-allocated buffer used for matching keyrings. */ +static char *ima_keyrings; +static size_t ima_keyrings_len; + static int ima_policy __initdata; static int __init default_measure_policy_setup(char *str) @@ -369,7 +373,7 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event, static bool ima_match_keyring(struct ima_rule_entry *rule, const char *keyring, const struct cred *cred) { - char *keyrings, *next_keyring, *keyrings_ptr; + char *next_keyring, *keyrings_ptr; bool matched = false; if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid)) @@ -381,15 +385,13 @@ static bool ima_match_keyring(struct ima_rule_entry *rule, if (!keyring) return false; - keyrings = kstrdup(rule->keyrings, GFP_KERNEL); - if (!keyrings) - return false; + strcpy(ima_keyrings, rule->keyrings); /* * "keyrings=" is specified in the policy in the format below: * keyrings=.builtin_trusted_keys|.ima|.evm */ - keyrings_ptr = keyrings; + keyrings_ptr = ima_keyrings; while ((next_keyring = strsep(&keyrings_ptr, "|")) != NULL) { if (!strcmp(next_keyring, keyring)) { matched = true; @@ -397,8 +399,6 @@ static bool ima_match_keyring(struct ima_rule_entry *rule, } } - kfree(keyrings); - return matched; } @@ -949,6 +949,7 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) bool uid_token; struct ima_template_desc *template_desc; int result = 0; + size_t keyrings_len; ab = integrity_audit_log_start(audit_context(), GFP_KERNEL, AUDIT_INTEGRITY_POLICY_RULE); @@ -1114,14 +1115,35 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) case Opt_keyrings: ima_log_string(ab, "keyrings", args[0].from); + keyrings_len = strlen(args[0].from) + 1; + if ((entry->keyrings) || (entry->action != MEASURE) || - (entry->func != KEY_CHECK)) { + (entry->func != KEY_CHECK) || + (keyrings_len < 2)) { result = -EINVAL; break; } + + if (keyrings_len > ima_keyrings_len) { + char *tmpbuf; + + tmpbuf = krealloc(ima_keyrings, keyrings_len, + GFP_KERNEL); + if (!tmpbuf) { + result = -ENOMEM; + break; + } + + ima_keyrings = tmpbuf; + ima_keyrings_len = keyrings_len; + } + entry->keyrings = kstrdup(args[0].from, GFP_KERNEL); if (!entry->keyrings) { + kfree(ima_keyrings); + ima_keyrings = NULL; + ima_keyrings_len = 0; result = -ENOMEM; break; }