From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8AB1EE14D8 for ; Sun, 10 Sep 2023 10:14:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345049AbjIJKOk (ORCPT ); Sun, 10 Sep 2023 06:14:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231314AbjIJKOj (ORCPT ); Sun, 10 Sep 2023 06:14:39 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89DAB1B9; Sun, 10 Sep 2023 03:14:35 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16153C433C8; Sun, 10 Sep 2023 10:14:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1694340875; bh=FcbyUTC8LwbVO6fXxkjxNDRy4yluvy9SqC6820WKn7E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=G32gfl1F0gvB0j9yuJ4msecfFMZqYrIKINC2z4TOfcW0tnwiAM2HhTaVU8W1wMOwH zOj7gXx2zM7/unXYC8VN6r3ZfrH/zIhuT5+JdZB+/+PFlXaTJZHLHBmW2LkrgmRCu+ DRERt+3JX+wMGsGt+WjMzUrGpUx+/VPwHdVGybMc/ERbQhgO/DDDBIawklF8OYUdKu /BMs41GKaTYvUAtLQwn1pj9zSmf/7qx550FBnlJIQ8UUmo8yWmGlRWhP/MFcgKLt3m jRSD83I6P6DFRH0eTZosD94RiuOVURdDeJYWB6ZOOSP9EF0xTuRG60ebgX33okCbg/ IF4+wJ4UzUgBw== Date: Sun, 10 Sep 2023 12:14:30 +0200 From: Christian Brauner To: Jeff Layton Cc: Alexander Viro , Trond Myklebust , Anna Schumaker , Ondrej Valousek , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH] fs: fix regression querying for ACL on fs's that don't support them Message-ID: <20230910-gingen-maulkorb-918c8c2ce6bf@brauner> References: <20230908-acl-fix-v1-1-1e6b76c8dcc8@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230908-acl-fix-v1-1-1e6b76c8dcc8@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 08, 2023 at 05:05:27PM -0400, Jeff Layton wrote: > In the not too distant past, the VFS ACL infrastructure would return > -EOPNOTSUPP on filesystems (like NFS) that set SB_POSIXACL but that > don't supply a get_acl or get_inode_acl method. On more recent kernels > this returns -ENODATA, which breaks one method of detecting when ACLs > are supported. > > Fix __get_acl to also check whether the inode has a "get_(inode_)?acl" > method and to just return -EOPNOTSUPP if not. > > Reported-by: Ondrej Valousek > Signed-off-by: Jeff Layton > --- > This patch is another approach to fixing this issue. I don't care too > much either way which approach we take, but this may fix the problem > for other filesystems too. Should we take a belt and suspenders > approach here and fix it in both places? > --- > fs/posix_acl.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/posix_acl.c b/fs/posix_acl.c > index a05fe94970ce..4c7c62040c43 100644 > --- a/fs/posix_acl.c > +++ b/fs/posix_acl.c > @@ -130,8 +130,12 @@ static struct posix_acl *__get_acl(struct mnt_idmap *idmap, > if (!is_uncached_acl(acl)) > return acl; > > - if (!IS_POSIXACL(inode)) > - return NULL; > + /* > + * NB: checking this after checking for a cached ACL allows tmpfs > + * (which doesn't specify a get_acl operation) to work properly. > + */ > + if (!IS_POSIXACL(inode) || (!inode->i_op->get_acl && !inode->i_op->get_inode_acl)) > + return ERR_PTR(-EOPNOTSUPP); Hmmm, I think that'll cause issues for permission checking during lookup: generic_permission() -> acl_permission_check() -> check_acl() -> get_inode_acl() -> __get_acl() // return ERR_PTR(-EOPNOTSUPP) instead of NULL Before this change this would've returned NULL and thus check_acl() would've returned EAGAIN which would've informed acl_permission_check() to continue with non-ACL based permission checking. Now you're going to error out with EOPNOTSUPP and cause permission checking to fallback to CAP_DAC_READ_SEARCH/CAP_DAC_OVERRIDE. So if you want this change you'll either need to change check_acl() as well. Unless I'm misreading.