From patchwork Wed Sep 28 23:29:27 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Gruenbacher X-Patchwork-Id: 9355179 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 960336077B for ; Wed, 28 Sep 2016 23:30:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 87D9329651 for ; Wed, 28 Sep 2016 23:30:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7C2B8296DE; Wed, 28 Sep 2016 23:30:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from oss.sgi.com (oss.sgi.com [192.48.182.195]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id C30D729651 for ; Wed, 28 Sep 2016 23:30:55 +0000 (UTC) Received: from oss.sgi.com (localhost [IPv6:::1]) by oss.sgi.com (Postfix) with ESMTP id 002307CD3; Wed, 28 Sep 2016 18:30:38 -0500 (CDT) X-Original-To: xfs@oss.sgi.com Delivered-To: xfs@oss.sgi.com Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id D04DB7CCD for ; Wed, 28 Sep 2016 18:30:36 -0500 (CDT) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay3.corp.sgi.com (Postfix) with ESMTP id 46C9AAC002 for ; Wed, 28 Sep 2016 16:30:36 -0700 (PDT) X-ASG-Debug-ID: 1475105429-0bf57c7e220e7a0001-NocioJ Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id TAECsJEpFh1PNYZL (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Wed, 28 Sep 2016 16:30:29 -0700 (PDT) X-Barracuda-Envelope-From: agruenba@redhat.com X-Barracuda-Effective-Source-IP: mx1.redhat.com[209.132.183.28] X-Barracuda-Apparent-Source-IP: 209.132.183.28 X-ASG-Whitelist: Client Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E74A7C0921B0; Wed, 28 Sep 2016 23:30:28 +0000 (UTC) Received: from nux.redhat.com (vpn1-4-153.ams2.redhat.com [10.36.4.153]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u8SNTfMv015711; Wed, 28 Sep 2016 19:30:24 -0400 From: Andreas Gruenbacher To: Alexander Viro Subject: [PATCH v26 08/21] richacl: Compute maximum file masks from an acl Date: Thu, 29 Sep 2016 01:29:27 +0200 X-ASG-Orig-Subj: [PATCH v26 08/21] richacl: Compute maximum file masks from an acl Message-Id: <1475105380-22837-9-git-send-email-agruenba@redhat.com> In-Reply-To: <1475105380-22837-1-git-send-email-agruenba@redhat.com> References: <1475105380-22837-1-git-send-email-agruenba@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 28 Sep 2016 23:30:29 +0000 (UTC) X-Barracuda-Connect: mx1.redhat.com[209.132.183.28] X-Barracuda-Start-Time: 1475105429 X-Barracuda-Encrypted: ECDHE-RSA-AES256-GCM-SHA384 X-Barracuda-URL: https://192.48.176.15:443/cgi-mod/mark.cgi X-Barracuda-Scan-Msg-Size: 6858 X-Barracuda-BRTS-Status: 1 X-Virus-Scanned: by bsmtpd at sgi.com Cc: "J. Bruce Fields" , linux-nfs@vger.kernel.org, Theodore Ts'o , Andreas Gruenbacher , linux-cifs@vger.kernel.org, linux-api@vger.kernel.org, Trond Myklebust , linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Christoph Hellwig , Andreas Dilger , linux-fsdevel@vger.kernel.org, Jeff Layton , linux-ext4@vger.kernel.org, Anna Schumaker X-BeenThere: xfs@oss.sgi.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com 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 Reviewed-by: Jeff Layton --- fs/richacl.c | 157 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 1 + 2 files changed, 158 insertions(+) diff --git a/fs/richacl.c b/fs/richacl.c index b7e96d0..0443090 100644 --- a/fs/richacl.c +++ b/fs/richacl.c @@ -303,3 +303,160 @@ out: return denied ? -EACCES : 0; } EXPORT_SYMBOL_GPL(richacl_permission); + +/* + * 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 of the group class + * + * 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 + * permissions allowed by the acl are disabled. + * + * We don't make assumptions about who the owner is so that the owner can + * change with no effect on the file masks or file mode permission bits; this + * means that we must assume that all entries can match the owner. + */ +void richacl_compute_max_masks(struct richacl *acl) +{ + 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)) { + 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_WRITE_THROUGH | RICHACL_MASKED); +} +EXPORT_SYMBOL_GPL(richacl_compute_max_masks); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index beeec35..700888b 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -178,5 +178,6 @@ 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(umode_t); extern int richacl_permission(struct inode *, const struct richacl *, int); +extern void richacl_compute_max_masks(struct richacl *); #endif /* __RICHACL_H */