Return-Path: Received: from mail-wi0-f171.google.com ([209.85.212.171]:36217 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932859AbbDXLF1 (ORCPT ); Fri, 24 Apr 2015 07:05:27 -0400 From: Andreas Gruenbacher To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org Cc: Andreas Gruenbacher Subject: [RFC v3 26/45] richacl: Move everyone@ aces down the acl Date: Fri, 24 Apr 2015 13:04:23 +0200 Message-Id: In-Reply-To: References: In-Reply-To: References: Sender: linux-nfs-owner@vger.kernel.org List-ID: The POSIX standard puts processes which are not the owner or a member in the owning group or which match any ace other then everyone@ on the other file class. We only know if a process is in the other class after processing the entire acl. Move all everyone@ aces in the acl down in the acl so that at most a single everyone@ allow ace remains at the end. Permissions which are not explicitly allowed are implicitly denied, so everyone@ deny ace is needed. The everyone@ aces can be moved down the acl without changing the permissions that the acl grants. This transformation simplifies the following algorithms, and eventually allows us to turn the final everyone@ allow ace into an entry for the other class. Signed-off-by: Andreas Gruenbacher --- fs/richacl_compat.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c index 2ea6658..63f4373 100644 --- a/fs/richacl_compat.c +++ b/fs/richacl_compat.c @@ -159,3 +159,68 @@ richace_change_mask(struct richacl_alloc *x, struct richace **ace, } return 0; } + +/** + * richacl_move_everyone_aces_down - move everyone@ aces to the end of the acl + * @x: acl and number of allocated entries + * + * Move all everyone aces to the end of the acl so that only a single everyone@ + * allow ace remains at the end, and update the mask fields of all aces on the + * way. The last ace of the resulting acl will be an everyone@ allow ace only + * if @acl grants any permissions to @everyone. No @everyone deny aces will + * remain. + * + * This transformation does not alter the permissions that the acl grants. + * Having at most one everyone@ allow ace at the end of the acl helps us in the + * following algorithms. + */ +static int +richacl_move_everyone_aces_down(struct richacl_alloc *x) +{ + struct richace *ace; + unsigned int allowed = 0, denied = 0; + + richacl_for_each_entry(ace, x->acl) { + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_everyone(ace)) { + if (richace_is_allow(ace)) + allowed |= (ace->e_mask & ~denied); + else if (richace_is_deny(ace)) + denied |= (ace->e_mask & ~allowed); + else + continue; + if (richace_change_mask(x, &ace, 0)) + return -1; + } else { + if (richace_is_allow(ace)) { + if (richace_change_mask(x, &ace, allowed | + (ace->e_mask & ~denied))) + return -1; + } else if (richace_is_deny(ace)) { + if (richace_change_mask(x, &ace, denied | + (ace->e_mask & ~allowed))) + return -1; + } + } + } + if (allowed & ~RICHACE_POSIX_ALWAYS_ALLOWED) { + struct richace *last_ace = ace - 1; + + if (x->acl->a_entries && + richace_is_everyone(last_ace) && + richace_is_allow(last_ace) && + richace_is_inherit_only(last_ace) && + last_ace->e_mask == allowed) + last_ace->e_flags &= ~RICHACE_INHERIT_ONLY_ACE; + else { + if (richacl_insert_entry(x, &ace)) + return -1; + ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE; + ace->e_flags = RICHACE_SPECIAL_WHO; + ace->e_mask = allowed; + ace->e_id.special = RICHACE_EVERYONE_SPECIAL_ID; + } + } + return 0; +} -- 2.1.0