Return-Path: Received: from mail-wi0-f174.google.com ([209.85.212.174]:38291 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964919AbbDXLFc (ORCPT ); Fri, 24 Apr 2015 07:05:32 -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 29/45] richacl: Apply the file masks to a richacl Date: Fri, 24 Apr 2015 13:04:26 +0200 Message-Id: <35b73e9515f2395c8595cbbf4ea7b92216e5e2a0.1429868795.git.agruenba@redhat.com> In-Reply-To: References: In-Reply-To: References: Sender: linux-nfs-owner@vger.kernel.org List-ID: Put all the pieces of the acl transformation puzzle together for computing a richacl which has the file masks "applied" so that the standard nfsv4 access check algorithm can be used on the richacl. Signed-off-by: Andreas Gruenbacher --- fs/richacl_compat.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 3 ++ 2 files changed, 106 insertions(+) diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c index 645917f..49af600 100644 --- a/fs/richacl_compat.c +++ b/fs/richacl_compat.c @@ -647,3 +647,106 @@ richacl_isolate_group_class(struct richacl_alloc *x) } return 0; } + +/** + * __richacl_apply_masks - apply the file masks to all aces + * @x: acl and number of allocated entries + * + * Apply the owner mask to owner@ aces, the other mask to + * everyone@ aces, and the group mask to all other aces. + * + * The previous transformations have brought the acl into a + * form in which applying the masks will not lead to the + * accidental loss of permissions anymore. + */ +static int +__richacl_apply_masks(struct richacl_alloc *x) +{ + struct richace *ace; + + richacl_for_each_entry(ace, x->acl) { + unsigned int mask; + + if (richace_is_inherit_only(ace) || !richace_is_allow(ace)) + continue; + if (richace_is_owner(ace)) + mask = x->acl->a_owner_mask; + else if (richace_is_everyone(ace)) + mask = x->acl->a_other_mask; + else + mask = x->acl->a_group_mask; + if (richace_change_mask(x, &ace, ace->e_mask & mask)) + return -1; + } + return 0; +} + +/** + * richacl_apply_masks - apply the masks to the acl + * + * Transform @acl so that the standard NFSv4 permission check algorithm (which + * is not aware of file masks) will compute the same access decisions as the + * richacl permission check algorithm (which looks at the acl and the file + * masks). + * + * This algorithm is split into several steps: + * + * - Move everyone@ aces to the end of the acl. This simplifies the other + * transformations, and allows the everyone@ allow ace at the end of the + * acl to eventually allow permissions to the other class only. + * + * - Propagate everyone@ permissions up the acl. This transformation makes + * sure that the owner and group class aces won't lose any permissions when + * we apply the other mask to the everyone@ allow ace at the end of the acl. + * + * - Apply the file masks to all aces. + * + * - Make sure that the owner is not granted any permissions beyond the owner + * mask from group class aces or from everyone@. + * + * - Make sure that the group class is not granted any permissions from + * everyone@. + * + * The algorithm is exact except for richacls which cannot be represented as an + * acl alone: for example, given this acl: + * + * group@:rw::allow + * + * when file masks corresponding to mode 0600 are applied, the owner would only + * get rw access if he is a member of the owning group. This algorithm would + * produce an empty acl in this case. We fix this case by modifying + * richacl_permission() so that the group mask is always applied to group class + * aces. With this fix, the owner would not have any access (beyond the + * implicit permissions always granted to owners). + * + * NOTE: Depending on the acl and file masks, this algorithm can increase the + * number of aces by almost a factor of three in the worst case. This may make + * the acl too large for some purposes. + */ +int +richacl_apply_masks(struct richacl **acl) +{ + if ((*acl)->a_flags & RICHACL_MASKED) { + struct richacl_alloc x = { + .acl = richacl_clone(*acl, GFP_KERNEL), + .count = (*acl)->a_count, + }; + if (!x.acl) + return -ENOMEM; + + if (richacl_move_everyone_aces_down(&x) || + richacl_propagate_everyone(&x) || + __richacl_apply_masks(&x) || + richacl_isolate_owner_class(&x) || + richacl_isolate_group_class(&x)) { + richacl_put(x.acl); + return -ENOMEM; + } + + x.acl->a_flags &= ~RICHACL_MASKED; + richacl_put(*acl); + *acl = x.acl; + } + return 0; +} +EXPORT_SYMBOL_GPL(richacl_apply_masks); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index bcc2b64..6a97dca 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -325,4 +325,7 @@ extern int richacl_equiv_mode(const struct richacl *, mode_t *); extern int richacl_permission(struct inode *, const struct richacl *, int); extern struct richacl *richacl_create(struct inode *, struct inode *); +/* richacl_compat.c */ +extern int richacl_apply_masks(struct richacl **); + #endif /* __RICHACL_H */ -- 2.1.0