From patchwork Wed Jul 22 13:02:58 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?Andreas_Gr=C3=BCnbacher?= X-Patchwork-Id: 6843831 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 8948D9F1D4 for ; Wed, 22 Jul 2015 13:22:53 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 79149206D5 for ; Wed, 22 Jul 2015 13:22:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52F82206D4 for ; Wed, 22 Jul 2015 13:22:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964986AbbGVNWs (ORCPT ); Wed, 22 Jul 2015 09:22:48 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:37396 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756647AbbGVNEO (ORCPT ); Wed, 22 Jul 2015 09:04:14 -0400 Received: by wibud3 with SMTP id ud3so171480117wib.0; Wed, 22 Jul 2015 06:04:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=Gxi1q9DyIqUSvZtNoshgv0W+VQCIZQF7SfGZBYT9w5s=; b=em6zq3eRm8GPhayJPdmvuIqlvMUGSh8O+EpIdtZ9VHlAjTPGqm0qKGkRm0Vvs4FRz/ XksOxAuAyHtlWc/v0vWDKkooe4O6JmCosyWRgDxrr6TEnpp2yoiXL7raYB5O/RxYsHu4 d7LyF1NgatNlt+IqIb7JLVio/fu4HmIIxNRu20ULAqhVU/rCmPlw0LhtsjSExWqXwIn0 h8NUeH6DUX84tEEQs+7PNVdYo8AzhXe1C0V/5VZedDst3YhnDgSDgRbkHQZXQgvkc/RQ LBw715f3fVyR0MLHNOVYZfA1tPbWxZ8i5yXe0/w5xPhdBnhimOYdsIC6V8ATGDdiieQI 62CQ== X-Received: by 10.180.74.162 with SMTP id u2mr42987390wiv.0.1437570251871; Wed, 22 Jul 2015 06:04:11 -0700 (PDT) Received: from schleppi.home.com ([149.14.88.26]) by smtp.gmail.com with ESMTPSA id u7sm21992628wif.3.2015.07.22.06.04.10 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Jul 2015 06:04:11 -0700 (PDT) From: Andreas Gruenbacher To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-api@vger.kernel.org, samba-technical@lists.samba.org, linux-security-module@vger.kernel.org, Andreas Gruenbacher Subject: [PATCH v5 08/39] richacl: Compute maximum file masks from an acl Date: Wed, 22 Jul 2015 15:02:58 +0200 Message-Id: <1437570209-29832-9-git-send-email-andreas.gruenbacher@gmail.com> X-Mailer: git-send-email 2.4.3 In-Reply-To: <1437570209-29832-1-git-send-email-andreas.gruenbacher@gmail.com> References: <1437570209-29832-1-git-send-email-andreas.gruenbacher@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-8.0 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Andreas Gruenbacher Compute upper bound owner, group, and other file masks with as few permissions as possible without denying any permissions that the NFSv4 acl in a richacl grants. This algorithm is used when a file inherits an acl at create time and when an acl is set via a mechanism that does not provide file masks (such as setting an acl via nfsd). When user-space sets an acl via setxattr, the extended attribute already includes the file masks. Setting an acl also sets the file mode permission bits: they are determined by the file masks; see richacl_masks_to_mode(). Signed-off-by: Andreas Gruenbacher Reviewed-by: J. Bruce Fields --- fs/richacl_base.c | 156 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 1 + 2 files changed, 157 insertions(+) diff --git a/fs/richacl_base.c b/fs/richacl_base.c index d12f984..23e9824 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -178,3 +178,159 @@ richacl_want_to_mask(unsigned int want) return mask; } EXPORT_SYMBOL_GPL(richacl_want_to_mask); + +/* + * Note: functions like richacl_allowed_to_who(), richacl_group_class_allowed(), + * and richacl_compute_max_masks() iterate through the entire acl in reverse + * order as an optimization. + * + * In the standard algorithm, aces are considered in forward order. When a + * process matches an ace, the permissions in the ace are either allowed or + * denied depending on the ace type. Once a permission has been allowed or + * denied, it is no longer considered in further aces. + * + * By iterating through the acl in reverse order, we can compute the same + * result without having to keep track of which permissions have been allowed + * and denied already. + */ + +/** + * richacl_allowed_to_who - permissions allowed to a specific who value + * + * Compute the maximum mask values allowed to a specific who value, taking + * everyone@ aces into account. + */ +static unsigned int richacl_allowed_to_who(struct richacl *acl, + struct richace *who) +{ + struct richace *ace; + unsigned int allowed = 0; + + richacl_for_each_entry_reverse(ace, acl) { + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_same_identifier(ace, who) || + richace_is_everyone(ace)) { + if (richace_is_allow(ace)) + allowed |= ace->e_mask; + else if (richace_is_deny(ace)) + allowed &= ~ace->e_mask; + } + } + return allowed; +} + +/** + * richacl_group_class_allowed - maximum permissions the group class is allowed + * + * Compute the maximum mask values allowed to a process in the group class + * (i.e., a process which is not the owner but is in the owning group or + * matches a user or group acl entry). This includes permissions granted or + * denied by everyone@ aces. + * + * See richacl_compute_max_masks(). + */ +static unsigned int richacl_group_class_allowed(struct richacl *acl) +{ + struct richace *ace; + unsigned int everyone_allowed = 0, group_class_allowed = 0; + int had_group_ace = 0; + + richacl_for_each_entry_reverse(ace, acl) { + if (richace_is_inherit_only(ace) || + richace_is_owner(ace)) + continue; + + if (richace_is_everyone(ace)) { + if (richace_is_allow(ace)) + everyone_allowed |= ace->e_mask; + else if (richace_is_deny(ace)) + everyone_allowed &= ~ace->e_mask; + } else { + group_class_allowed |= + richacl_allowed_to_who(acl, ace); + + if (richace_is_group(ace)) + had_group_ace = 1; + } + } + /* + * If the acl doesn't contain any group@ aces, richacl_allowed_to_who() + * wasn't called for the owning group. We could make that call now, but + * we already know the result (everyone_allowed). + */ + if (!had_group_ace) + group_class_allowed |= everyone_allowed; + return group_class_allowed; +} + +/** + * richacl_compute_max_masks - compute upper bound masks + * + * Computes upper bound owner, group, and other masks so that none of + * the mask flags allowed by the acl are disabled (for any choice of the + * file owner or group membership). + */ +void richacl_compute_max_masks(struct richacl *acl, kuid_t owner) +{ + unsigned int gmask = ~0; + struct richace *ace; + + /* + * @gmask contains all permissions which the group class is ever + * allowed. We use it to avoid adding permissions to the group mask + * from everyone@ allow aces which the group class is always denied + * through other aces. For example, the following acl would otherwise + * result in a group mask of rw: + * + * group@:w::deny + * everyone@:rw::allow + * + * Avoid computing @gmask for acls which do not include any group class + * deny aces: in such acls, the group class is never denied any + * permissions from everyone@ allow aces, and the group class cannot + * have fewer permissions than the other class. + */ + +restart: + acl->a_owner_mask = 0; + acl->a_group_mask = 0; + acl->a_other_mask = 0; + + richacl_for_each_entry_reverse(ace, acl) { + if (richace_is_inherit_only(ace)) + continue; + + if (richace_is_owner(ace) || + (richace_is_unix_user(ace) && + uid_eq(ace->e_id.uid, owner))) { + if (richace_is_allow(ace)) + acl->a_owner_mask |= ace->e_mask; + else if (richace_is_deny(ace)) + acl->a_owner_mask &= ~ace->e_mask; + } else if (richace_is_everyone(ace)) { + if (richace_is_allow(ace)) { + acl->a_owner_mask |= ace->e_mask; + acl->a_group_mask |= ace->e_mask & gmask; + acl->a_other_mask |= ace->e_mask; + } else if (richace_is_deny(ace)) { + acl->a_owner_mask &= ~ace->e_mask; + acl->a_group_mask &= ~ace->e_mask; + acl->a_other_mask &= ~ace->e_mask; + } + } else { + if (richace_is_allow(ace)) { + acl->a_owner_mask |= ace->e_mask & gmask; + acl->a_group_mask |= ace->e_mask & gmask; + } else if (richace_is_deny(ace) && gmask == ~0) { + gmask = richacl_group_class_allowed(acl); + if (likely(gmask != ~0)) + /* should always be true */ + goto restart; + } + } + } + + acl->a_flags &= ~RICHACL_MASKED; +} +EXPORT_SYMBOL_GPL(richacl_compute_max_masks); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index 1ae0bf8..90baca3 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -301,5 +301,6 @@ extern void richace_copy(struct richace *, const struct richace *); extern int richacl_masks_to_mode(const struct richacl *); extern unsigned int richacl_mode_to_mask(mode_t); extern unsigned int richacl_want_to_mask(unsigned int); +extern void richacl_compute_max_masks(struct richacl *, kuid_t); #endif /* __RICHACL_H */