| Message ID | 75f97eb880b1bbb47b0aa146d3f528e32de06744.1427471526.git.agruenba@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Mar 27, 2015 at 05:50:09PM +0100, Andreas Gruenbacher wrote: > 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 specify file modes > (such as via nfsd). When user-space sets an acl, the file masks are > passed in as part of the xattr. > > When setting a richacl, the file masks determine what the file > permission bits will be set to; see richacl_masks_to_mode(). > > Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> > --- > fs/richacl_base.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/richacl.h | 1 + > 2 files changed, 129 insertions(+) > > diff --git a/fs/richacl_base.c b/fs/richacl_base.c > index 9cd15ca..d9e557a 100644 > --- a/fs/richacl_base.c > +++ b/fs/richacl_base.c > @@ -173,3 +173,131 @@ richacl_want_to_mask(unsigned int want) > return mask; > } > EXPORT_SYMBOL_GPL(richacl_want_to_mask); > + > +/** > + * richacl_allowed_to_who - mask flags allowed to a specific who value > + * > + * Computes the mask values allowed to a specific who value, taking > + * EVERYONE@ entries 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 > + * > + * 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 (!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) > +{ > + 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 or 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. > + */ Cripes, by the time I got to this point I'd already written one response where I complained this was wrong, another where I explained why it was right, and gone back and forth a couple more times. Feel free to add a Reviewed-by: J. Bruce Fields <bfields@redhat.com> but maybe we could use a couple more examples here. Or a paper. --b. > + > +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_MASKED; > +} > +EXPORT_SYMBOL_GPL(richacl_compute_max_masks); > diff --git a/include/linux/richacl.h b/include/linux/richacl.h > index 2120aa6..25f45f7 100644 > --- a/include/linux/richacl.h > +++ b/include/linux/richacl.h > @@ -288,5 +288,6 @@ extern struct richacl *richacl_alloc(int, 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 *); > > #endif /* __RICHACL_H */ > -- > 2.1.0 > > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2015-04-20 23:28 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>: > Cripes, by the time I got to this point I'd already written one response > where I complained this was wrong, another where I explained why it was > right, and gone back and forth a couple more times. > > Feel free to add a > > Reviewed-by: J. Bruce Fields <bfields@redhat.com> > > but maybe we could use a couple more examples here. Or a paper. Thanks, I've tried to explain things a little better in the updated patch queue just pushed out. Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/richacl_base.c b/fs/richacl_base.c index 9cd15ca..d9e557a 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -173,3 +173,131 @@ richacl_want_to_mask(unsigned int want) return mask; } EXPORT_SYMBOL_GPL(richacl_want_to_mask); + +/** + * richacl_allowed_to_who - mask flags allowed to a specific who value + * + * Computes the mask values allowed to a specific who value, taking + * EVERYONE@ entries 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 + * + * 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 (!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) +{ + 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 or 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. + */ + +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_MASKED; +} +EXPORT_SYMBOL_GPL(richacl_compute_max_masks); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index 2120aa6..25f45f7 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -288,5 +288,6 @@ extern struct richacl *richacl_alloc(int, 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 *); #endif /* __RICHACL_H */
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 specify file modes (such as via nfsd). When user-space sets an acl, the file masks are passed in as part of the xattr. When setting a richacl, the file masks determine what the file permission bits will be set to; see richacl_masks_to_mode(). Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> --- fs/richacl_base.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 1 + 2 files changed, 129 insertions(+)