Return-Path: Received: from fieldses.org ([173.255.197.46]:48545 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752661AbbIKUfb (ORCPT ); Fri, 11 Sep 2015 16:35:31 -0400 Date: Fri, 11 Sep 2015 16:35:30 -0400 To: Andreas Gruenbacher 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 Subject: Re: [RFC v7 09/41] richacl: Update the file masks in chmod() Message-ID: <20150911203530.GE11677@fieldses.org> References: <1441448856-13478-1-git-send-email-agruenba@redhat.com> <1441448856-13478-10-git-send-email-agruenba@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1441448856-13478-10-git-send-email-agruenba@redhat.com> From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sat, Sep 05, 2015 at 12:27:04PM +0200, Andreas Gruenbacher wrote: > Doing a chmod() sets the file mode, which includes the file permission > bits. When a file has a richacl, the permissions that the richacl > grants need to be limited to what the new file permission bits allow. > > This is done by setting the file masks in the richacl to what the file > permission bits map to. The richacl access check algorithm takes the > file masks into account, which ensures that the richacl cannot grant too > many permissions. > > It is possible to explicitly add permissions to the file masks which go > beyond what the file permission bits can grant (like the > RICHACE_WRITE_ACL permission). The POSIX.1 standard calls this an > alternate file access control mechanism. A subsequent chmod() would > ensure that those permissions are disabled again. > Reviewed-by: J. Bruce Fields > Signed-off-by: Andreas Gruenbacher > --- > fs/richacl_base.c | 40 ++++++++++++++++++++++++++++++++++++++++ > include/linux/richacl.h | 1 + > 2 files changed, 41 insertions(+) > > diff --git a/fs/richacl_base.c b/fs/richacl_base.c > index fc544f7..6c69234 100644 > --- a/fs/richacl_base.c > +++ b/fs/richacl_base.c > @@ -339,3 +339,43 @@ restart: > acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); > } > EXPORT_SYMBOL_GPL(richacl_compute_max_masks); > + > +/** > + * richacl_chmod - update the file masks to reflect the new mode > + * @mode: new file permission bits including the file type > + * > + * Return a copy of @acl where the file masks have been replaced by the file > + * masks corresponding to the file permission bits in @mode, or returns @acl > + * itself if the file masks are already up to date. Takes over a reference > + * to @acl. > + */ > +struct richacl * > +richacl_chmod(struct richacl *acl, mode_t mode) > +{ > + unsigned int x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD; > + unsigned int owner_mask, group_mask, other_mask; > + struct richacl *clone; > + > + owner_mask = richacl_mode_to_mask(mode >> 6) & ~x; > + group_mask = richacl_mode_to_mask(mode >> 3) & ~x; > + other_mask = richacl_mode_to_mask(mode) & ~x; > + > + if (acl->a_owner_mask == owner_mask && > + acl->a_group_mask == group_mask && > + acl->a_other_mask == other_mask && > + (acl->a_flags & (RICHACL_WRITE_THROUGH | RICHACL_MASKED))) > + return acl; > + > + clone = richacl_clone(acl, GFP_KERNEL); > + richacl_put(acl); > + if (!clone) > + return ERR_PTR(-ENOMEM); > + > + clone->a_flags |= (RICHACL_WRITE_THROUGH | RICHACL_MASKED); > + clone->a_owner_mask = owner_mask; > + clone->a_group_mask = group_mask; > + clone->a_other_mask = other_mask; > + > + return clone; > +} > +EXPORT_SYMBOL_GPL(richacl_chmod); > diff --git a/include/linux/richacl.h b/include/linux/richacl.h > index e81144a..e00f313 100644 > --- a/include/linux/richacl.h > +++ b/include/linux/richacl.h > @@ -298,5 +298,6 @@ 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 *); > +extern struct richacl *richacl_chmod(struct richacl *, mode_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