From patchwork Wed Jun 24 21:56:57 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: 6670941 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 09EE59F39B for ; Wed, 24 Jun 2015 22:06:39 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 075E82056E for ; Wed, 24 Jun 2015 22:06:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D39BB20569 for ; Wed, 24 Jun 2015 22:06:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753975AbbFXWGJ (ORCPT ); Wed, 24 Jun 2015 18:06:09 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:33991 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752130AbbFXV5o (ORCPT ); Wed, 24 Jun 2015 17:57:44 -0400 Received: by wicnd19 with SMTP id nd19so1110124wic.1; Wed, 24 Jun 2015 14:57:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:subject:date:message-id:in-reply-to:references; bh=jeUfgOKLwSZokSIUio2hxquYzhT68RmdpzdhL93anVA=; b=Xp/WlPYl6gw93jnTIjChHaWfi+j/rwh4cntyfFQ3iowqn+2knYO0mhFc1QiwDff7hz NSeJ8hB5UvC3SL66Cs8lLuckAgxWMhHd6Uw4oYrj+vvECyxOPdP0zvYEZ2765veQiTBW EGpaH0en2GrrJJ0/vcgSXUnY4KpiGPJCzzIt0KztqrK0/8exTFpW1zOYkn0DztWHU5X7 1+ipkpWcLU3z/vKh0UI6stoXcDevDbwUnT5cU19NGHIg3gUbHc+4gM0N8Id7zQJMcXzK vju8Fp4UthOtqqClfrXhrZCV22MnxIunZdfU5GIazN+kx2QDzeMxzmaJP0K+BZP/4Hqx Z2yw== X-Received: by 10.180.187.41 with SMTP id fp9mr8780873wic.67.1435183062071; Wed, 24 Jun 2015 14:57:42 -0700 (PDT) Received: from nuc.home.com (80-110-112-232.cgn.dynamic.surfer.at. [80.110.112.232]) by mx.google.com with ESMTPSA id lu5sm42559880wjb.9.2015.06.24.14.57.40 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jun 2015 14:57:41 -0700 (PDT) From: Andreas Gruenbacher X-Google-Original-From: Andreas Gruenbacher To: linux-kernel@vger.kernel.org, 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 Subject: [RFC v4 08/31] richacl: Compute maximum file masks from an acl Date: Wed, 24 Jun 2015 23:56:57 +0200 Message-Id: <1435183040-22726-9-git-send-email-agruenba@redhat.com> X-Mailer: git-send-email 2.4.2 In-Reply-To: <1435183040-22726-1-git-send-email-agruenba@redhat.com> References: <1435183040-22726-1-git-send-email-agruenba@redhat.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=-5.7 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, SUSPICIOUS_RECIPS, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=unavailable 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 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 032c756..fda0568 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -169,3 +169,159 @@ 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 7957bbf..3cea47a 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -300,5 +300,6 @@ extern struct richacl *richacl_clone(const struct richacl *, gfp_t); 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 */