From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DCCF9C433DF for ; Thu, 28 May 2020 12:05:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BDF3721548 for ; Thu, 28 May 2020 12:05:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590667539; bh=prOMc/RStpaK3YUH4KzHyr5ESVXotKLWP1/xmvu8a7w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=GzZZ8uQfdTRONEHVNursYhKmoLom+1J4rrU5COFQHKI29bZzupZjeXJbu9aEytVDu CMc7oQknzzGvp9ptRMxs6qU44TvdhI0NawTZqlVmTPlZjQgU+K7oDdxHw4wtzC/l4E HzH1/cCu7mfUk3sRB/MzQEO3De5MgsNBoWI6djJQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389309AbgE1MFb (ORCPT ); Thu, 28 May 2020 08:05:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:49304 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388746AbgE1L47 (ORCPT ); Thu, 28 May 2020 07:56:59 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C1ED32158C; Thu, 28 May 2020 11:56:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590667018; bh=prOMc/RStpaK3YUH4KzHyr5ESVXotKLWP1/xmvu8a7w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ew3Hp2CiAAFPfGhjVISk9gRB1awnu9QBcOqXAAhWyNy7954ADKWkcrtBPi22F28ne /fTisDf45FRPOtkVvVyYvWdyc918DYDKQgakk/kzQodh5Eb7AiqNQzqC57P67iYhkK TY90Vzf+syJL/WlX6fmixk/tCIoyE0mWfjQEE44M= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Madhuparna Bhowmik , kernel test robot , "Paul E . McKenney" , Mimi Zohar , Sasha Levin , linux-ima-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 03/26] evm: Fix RCU list related warnings Date: Thu, 28 May 2020 07:56:31 -0400 Message-Id: <20200528115654.1406165-3-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200528115654.1406165-1-sashal@kernel.org> References: <20200528115654.1406165-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: From: Madhuparna Bhowmik [ Upstream commit 770f60586d2af0590be263f55fd079226313922c ] This patch fixes the following warning and few other instances of traversal of evm_config_xattrnames list: [ 32.848432] ============================= [ 32.848707] WARNING: suspicious RCU usage [ 32.848966] 5.7.0-rc1-00006-ga8d5875ce5f0b #1 Not tainted [ 32.849308] ----------------------------- [ 32.849567] security/integrity/evm/evm_main.c:231 RCU-list traversed in non-reader section!! Since entries are only added to the list and never deleted, use list_for_each_entry_lockless() instead of list_for_each_entry_rcu for traversing the list. Also, add a relevant comment in evm_secfs.c to indicate this fact. Reported-by: kernel test robot Suggested-by: Paul E. McKenney Signed-off-by: Madhuparna Bhowmik Acked-by: Paul E. McKenney (RCU viewpoint) Signed-off-by: Mimi Zohar Signed-off-by: Sasha Levin --- security/integrity/evm/evm_crypto.c | 2 +- security/integrity/evm/evm_main.c | 4 ++-- security/integrity/evm/evm_secfs.c | 9 ++++++++- 3 files changed, 11 insertions(+), 4 deletions(-) diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index cc826c2767a3..fbc2ee6d46fc 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -209,7 +209,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry, data->hdr.length = crypto_shash_digestsize(desc->tfm); error = -ENODATA; - list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) { + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { bool is_ima = false; if (strcmp(xattr->name, XATTR_NAME_IMA) == 0) diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index f9a81b187fae..a2c393385db0 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -99,7 +99,7 @@ static int evm_find_protected_xattrs(struct dentry *dentry) if (!(inode->i_opflags & IOP_XATTR)) return -EOPNOTSUPP; - list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) { + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0); if (error < 0) { if (error == -ENODATA) @@ -230,7 +230,7 @@ static int evm_protected_xattr(const char *req_xattr_name) struct xattr_list *xattr; namelen = strlen(req_xattr_name); - list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) { + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { if ((strlen(xattr->name) == namelen) && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) { found = 1; diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c index c11c1f7b3ddd..0f37ef27268d 100644 --- a/security/integrity/evm/evm_secfs.c +++ b/security/integrity/evm/evm_secfs.c @@ -234,7 +234,14 @@ static ssize_t evm_write_xattrs(struct file *file, const char __user *buf, goto out; } - /* Guard against races in evm_read_xattrs */ + /* + * xattr_list_mutex guards against races in evm_read_xattrs(). + * Entries are only added to the evm_config_xattrnames list + * and never deleted. Therefore, the list is traversed + * using list_for_each_entry_lockless() without holding + * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs() + * and evm_protected_xattr(). + */ mutex_lock(&xattr_list_mutex); list_for_each_entry(tmp, &evm_config_xattrnames, list) { if (strcmp(xattr->name, tmp->name) == 0) { -- 2.25.1