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=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,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 0E98DC072B1 for ; Thu, 30 May 2019 04:48:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB65E25C54 for ; Thu, 30 May 2019 04:48:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559191690; bh=i5fi8eeImd4CC6+5pIfflGo+RRsZPt9AiRTjEx8MsPo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=s1Ih+XyOKkDCT1SmyVn1leJArdpOlfQRgeEpgltN8zlANZtUy1VU+DOERp5IJC40i 6DmUIK2sAhE+XQYdo3PzK40jhVxYTfw9LPPUcpV9/qiJMQ3VOd7p+lSvcSwSD/8Exc 7XiJnSfgbmbRPljNmS12hDFd9251A8qhBiTdCvik= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728526AbfE3DLY (ORCPT ); Wed, 29 May 2019 23:11:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:50644 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728513AbfE3DLY (ORCPT ); Wed, 29 May 2019 23:11:24 -0400 Received: from localhost (ip67-88-213-2.z213-88-67.customer.algx.net [67.88.213.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 76ABF244CB; Thu, 30 May 2019 03:11:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559185883; bh=i5fi8eeImd4CC6+5pIfflGo+RRsZPt9AiRTjEx8MsPo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=giPeEqskh41+gTVYac5Rur+jz02r6VWf95eA19Q73dCMpjVsK1GAVhg2rrq5qj4qp hHxqEa6J8CwKw1KXsdBTiYJrq65tqwrhOve/0S8quTHaYHt51RuGmKGKAR4WmPA1yh 6Bn3qFvrrPeyUZ64nkQT15VmfN2UpFQcEZwi+9yw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Biggers , Theodore Tso , Sasha Levin Subject: [PATCH 5.1 192/405] fscrypt: use READ_ONCE() to access ->i_crypt_info Date: Wed, 29 May 2019 20:03:10 -0700 Message-Id: <20190530030550.721489349@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030540.291644921@linuxfoundation.org> References: <20190530030540.291644921@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org [ Upstream commit e37a784d8b6a1e726de5ddc7b4809c086a08db09 ] ->i_crypt_info starts out NULL and may later be locklessly set to a non-NULL value by the cmpxchg() in fscrypt_get_encryption_info(). But ->i_crypt_info is used directly, which technically is incorrect. It's a data race, and it doesn't include the data dependency barrier needed to safely dereference the pointer on at least one architecture. Fix this by using READ_ONCE() instead. Note: we don't need to use smp_load_acquire(), since dereferencing the pointer only requires a data dependency barrier, which is already included in READ_ONCE(). We also don't need READ_ONCE() in places where ->i_crypt_info is unconditionally dereferenced, since it must have already been checked. Also downgrade the cmpxchg() to cmpxchg_release(), since RELEASE semantics are sufficient on the write side. Signed-off-by: Eric Biggers Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/crypto/crypto.c | 2 +- fs/crypto/fname.c | 4 ++-- fs/crypto/keyinfo.c | 4 ++-- fs/crypto/policy.c | 6 +++--- include/linux/fscrypt.h | 3 ++- 5 files changed, 10 insertions(+), 9 deletions(-) diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 4dc788e3bc96b..fe38b53060454 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -334,7 +334,7 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) spin_lock(&dentry->d_lock); cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY; spin_unlock(&dentry->d_lock); - dir_has_key = (d_inode(dir)->i_crypt_info != NULL); + dir_has_key = fscrypt_has_encryption_key(d_inode(dir)); dput(dir); /* diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index 7ff40a73dbece..050384c79f40e 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -269,7 +269,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode, if (iname->len < FS_CRYPTO_BLOCK_SIZE) return -EUCLEAN; - if (inode->i_crypt_info) + if (fscrypt_has_encryption_key(inode)) return fname_decrypt(inode, iname, oname); if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) { @@ -336,7 +336,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, if (ret) return ret; - if (dir->i_crypt_info) { + if (fscrypt_has_encryption_key(dir)) { if (!fscrypt_fname_encrypted_size(dir, iname->len, dir->i_sb->s_cop->max_namelen, &fname->crypto_buf.len)) diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 322ce9686bdba..bf291c10c682f 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -509,7 +509,7 @@ int fscrypt_get_encryption_info(struct inode *inode) u8 *raw_key = NULL; int res; - if (inode->i_crypt_info) + if (fscrypt_has_encryption_key(inode)) return 0; res = fscrypt_initialize(inode->i_sb->s_cop->flags); @@ -573,7 +573,7 @@ int fscrypt_get_encryption_info(struct inode *inode) if (res) goto out; - if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) + if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) crypt_info = NULL; out: if (res == -ENOKEY) diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index bd7eaf9b3f003..d536889ac31bf 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -194,8 +194,8 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) res = fscrypt_get_encryption_info(child); if (res) return 0; - parent_ci = parent->i_crypt_info; - child_ci = child->i_crypt_info; + parent_ci = READ_ONCE(parent->i_crypt_info); + child_ci = READ_ONCE(child->i_crypt_info); if (parent_ci && child_ci) { return memcmp(parent_ci->ci_master_key_descriptor, @@ -246,7 +246,7 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child, if (res < 0) return res; - ci = parent->i_crypt_info; + ci = READ_ONCE(parent->i_crypt_info); if (ci == NULL) return -ENOKEY; diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index e5194fc3983e9..08246f068fd89 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -79,7 +79,8 @@ struct fscrypt_ctx { static inline bool fscrypt_has_encryption_key(const struct inode *inode) { - return (inode->i_crypt_info != NULL); + /* pairs with cmpxchg_release() in fscrypt_get_encryption_info() */ + return READ_ONCE(inode->i_crypt_info) != NULL; } static inline bool fscrypt_dummy_context_enabled(struct inode *inode) -- 2.20.1