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From: Vivek Goyal <vgoyal@redhat.com>
To: Bruce Fields <bfields@redhat.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	viro@zeniv.linux.org.uk, virtio-fs@redhat.com, dwalsh@redhat.com,
	dgilbert@redhat.com, casey.schaufler@intel.com,
	linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
	tytso@mit.edu, miklos@szeredi.hu, gscrivan@redhat.com,
	jack@suse.cz, Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v2 1/1] xattr: Allow user.* xattr on symlink and special files
Date: Mon, 12 Jul 2021 10:02:47 -0400	[thread overview]
Message-ID: <20210712140247.GA486376@redhat.com> (raw)
In-Reply-To: <CAPL3RVGKg4G5qiiHo7KYPcsWWgeoW=qNPOSQpd3Sv329jrWrLQ@mail.gmail.com>

On Fri, Jul 09, 2021 at 04:10:16PM -0400, Bruce Fields wrote:
> On Fri, Jul 9, 2021 at 1:59 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> > nfs seems to have some issues.
> 
> I'm not sure what the expected behavior is for nfs.  All I have for
> now is some generic troubleshooting ideas, sorry:
> 
> > - I can set user.foo xattr on symlink and query it back using xattr name.
> >
> >   getfattr -h -n user.foo foo-link.txt
> >
> >   But when I try to dump all xattrs on this file, user.foo is being
> >   filtered out it looks like. Not sure why.
> 
> Logging into the server and seeing what's set there could help confirm
> whether it's the client or server that's at fault.  (Or watching the
> traffic in wireshark; there are GET/SET/LISTXATTR ops that should be
> easy to spot.)
> 
> > - I can't set "user.foo" xattr on a device node on nfs and I get
> >   "Permission denied". I am assuming nfs server is returning this.
> 
> Wireshark should tell you whether it's the server or client doing that.
> 
> The RFC is https://datatracker.ietf.org/doc/html/rfc8276, and I don't
> see any explicit statement about what the server should do in the case
> of symlinks or device nodes, but I do see "Any regular file or
> directory may have a set of extended attributes", so that was clearly
> the assumption.  Also, NFS4ERR_WRONG_TYPE is listed as a possible
> error return for the xattr ops.  But on a quick skim I don't see any
> explicit checks in the nfsd code, so I *think* it's just relying on
> the vfs for any file type checks.

Hi Bruce,

Thanks for the response. I am just trying to do set a user.foo xattr on
a device node on nfs.

setfattr -n "user.foo" -v "bar" /mnt/nfs/test-dev

and I get -EACCESS.

I put some printk() statements and EACCESS is being returned from here.

nfs4_xattr_set_nfs4_user() {
        if (!nfs_access_get_cached(inode, current_cred(), &cache, true)) {
                if (!(cache.mask & NFS_ACCESS_XAWRITE)) {
                        return -EACCES;
                }
        }
}

Value of cache.mask=0xd at the time of error.

Thanks
Vivek


  reply	other threads:[~2021-07-12 14:03 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-08 17:57 [RFC PATCH v2 0/1] Relax restrictions on user.* xattr Vivek Goyal
2021-07-08 17:57 ` [PATCH v2 1/1] xattr: Allow user.* xattr on symlink and special files Vivek Goyal
2021-07-09  9:19   ` Christian Brauner
2021-07-09 15:27     ` Vivek Goyal
2021-07-09 15:34       ` Casey Schaufler
2021-07-09 17:59         ` Vivek Goyal
2021-07-09 20:10           ` Bruce Fields
2021-07-12 14:02             ` Vivek Goyal [this message]
2021-07-12 15:41               ` J. Bruce Fields
2021-07-12 17:47                 ` Vivek Goyal
2021-07-12 19:31                   ` J. Bruce Fields
2021-07-12 21:22                     ` Vivek Goyal
2021-07-13 14:17                   ` Casey Schaufler
2021-08-30 18:45                     ` Vivek Goyal
2021-07-09 20:36         ` Theodore Ts'o
2021-07-12 17:50           ` Vivek Goyal
2021-07-12 12:49         ` [Virtio-fs] " Greg Kurz
2021-07-13 14:28           ` Casey Schaufler
2021-07-09 16:00 ` [RFC PATCH v2 0/1] Relax restrictions on user.* xattr Daniel Walsh

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