linux-kernel - Re: [PATCH v2 2/2] nfs: NFSv3: fix SGID bit dropped when inheriting ACLs

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Date:   Thu, 24 Jun 2021 23:48:11 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Trond Myklebust <trondmy@...merspace.com>
Cc:     "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "joseph.qi@...ux.alibaba.com" <joseph.qi@...ux.alibaba.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "agruenba@...hat.com" <agruenba@...hat.com>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>
Subject: Re: [PATCH v2 2/2] nfs: NFSv3: fix SGID bit dropped when inheriting
 ACLs

Hi Trond,

On Thu, Jun 24, 2021 at 01:13:50PM +0000, Trond Myklebust wrote:
> On Wed, 2021-06-23 at 14:38 +0800, Gao Xiang wrote:
> > generic/444 fails with NFSv3 as shown above, "
> >      QA output created by 444
> >      drwxrwsr-x
> >     -drwxrwsr-x
> >     +drwxrwxr-x
> > ", which tests "SGID inheritance with default ACLs" fs regression
> > and looks after the following commits:
> > 
> > a3bb2d558752 ("ext4: Don't clear SGID when inheriting ACLs")
> > 073931017b49 ("posix_acl: Clear SGID bit when setting file
> > permissions")
> > 
> > commit 055ffbea0596 ("[PATCH] NFS: Fix handling of the umask when
> > an NFSv3 default acl is present.") sets acls explicitly when
> > when files are created in a directory that has a default ACL.
> > However, after commit a3bb2d558752 and 073931017b49, SGID can be
> > dropped if user is not member of the owning group with
> > set_posix_acl() called.
> > 
> > Since underlayfs will handle ACL inheritance when creating
> > files in a directory that has the default ACL and the umask is
> > supposed to be ignored for such case. Therefore, I think no need
> > to set acls explicitly (to avoid SGID bit cleared) but only apply
> > client umask if the default ACL of the parent directory doesn't
> > exist.
> 
> Hmm... Has this patch been tested with a Solaris server? Your assertion
> above appears to be true for Linux servers, but this code needs to
> interoperate with non-Linux draft posix acl compatible servers too.

Sigh.. I'm not quite sure about the Solaris side since I don't have
the environment. In principle, I just think ACL inheritance should
be an underlayfs behavior rather than some nfs-specific behavior
so I assume no risk with this patch applied.

With my premature short-time glance about illumos nfs client
implementation, I don't find such setacl call  (correct me if
I'm missing...) 
https://github.com/illumos/illumos-gate/blob/9ecd05bdc59e4a1091c51ce68cce2028d5ba6fd1/usr/src/uts/common/fs/nfs/nfs3_vnops.c#L2224

(And if someone has such Solaris environment, it would be much
 helpful to check this...)

> 
> I've already taken the other patch in this series, since that one
> appears correct, and doesn't have any interoperability consequences.

Thanks all!

Thanks,
Gao Xiang

> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@...merspace.com
> 
>