From mboxrd@z Thu Jan 1 00:00:00 1970 From: bfields@fieldses.org (J. Bruce Fields) Subject: Re: [RFC v7 26/41] richacl: Apply the file masks to a richacl Date: Tue, 22 Sep 2015 15:11:08 -0400 Message-ID: <20150922191108.GC19127@fieldses.org> References: <1441448856-13478-1-git-send-email-agruenba@redhat.com> <1441448856-13478-27-git-send-email-agruenba@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-api@vger.kernel.org, linux-cifs@vger.kernel.org, linux-security-module@vger.kernel.org, Andreas Gruenbacher To: Andreas Gruenbacher Return-path: Content-Disposition: inline In-Reply-To: <1441448856-13478-27-git-send-email-agruenba@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Sat, Sep 05, 2015 at 12:27:21PM +0200, Andreas Gruenbacher wrote: > 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 | 110 ++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/richacl.h | 3 ++ > 2 files changed, 113 insertions(+) > > diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c > index 412844c..9681efe 100644 > --- a/fs/richacl_compat.c > +++ b/fs/richacl_compat.c > @@ -730,3 +730,113 @@ richacl_isolate_group_class(struct richacl_alloc *alloc) > } > return 0; > } > + > +/** > + * __richacl_apply_masks - apply the file masks to all aces > + * @alloc: 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 *alloc, kuid_t owner) > +{ > + struct richace *ace; > + > + richacl_for_each_entry(ace, alloc->acl) { > + unsigned int mask; > + > + if (richace_is_inherit_only(ace) || !richace_is_allow(ace)) > + continue; > + if (richace_is_owner(ace) || > + (richace_is_unix_user(ace) && uid_eq(owner, ace->e_id.uid))) > + mask = alloc->acl->a_owner_mask; Is treating matching user aces like owner aces what you intended to do, and if so, why? --b. > + else if (richace_is_everyone(ace)) > + mask = alloc->acl->a_other_mask; > + else > + mask = alloc->acl->a_group_mask; > + if (richace_change_mask(alloc, &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 the owner is granted the owner mask permissions. > + * > + * - Make sure everyone is granted the other mask permissions. > + * > + * - 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, kuid_t owner) > +{ > + if ((*acl)->a_flags & RICHACL_MASKED) { > + struct richacl_alloc alloc = { > + .acl = richacl_clone(*acl, GFP_KERNEL), > + .count = (*acl)->a_count, > + }; > + if (!alloc.acl) > + return -ENOMEM; > + > + if (richacl_move_everyone_aces_down(&alloc) || > + richacl_propagate_everyone(&alloc) || > + __richacl_apply_masks(&alloc, owner) || > + richacl_set_owner_permissions(&alloc) || > + richacl_set_other_permissions(&alloc) || > + richacl_isolate_owner_class(&alloc) || > + richacl_isolate_group_class(&alloc)) { > + richacl_put(alloc.acl); > + return -ENOMEM; > + } > + > + alloc.acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); > + richacl_put(*acl); > + *acl = alloc.acl; > + } > + return 0; > +} > +EXPORT_SYMBOL_GPL(richacl_apply_masks); > diff --git a/include/linux/richacl.h b/include/linux/richacl.h > index 832b06c..a945f3c 100644 > --- a/include/linux/richacl.h > +++ b/include/linux/richacl.h > @@ -332,4 +332,7 @@ extern struct richacl *richacl_inherit(const struct richacl *, int); > 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 **, kuid_t); > + > #endif /* __RICHACL_H */ > -- > 2.4.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html