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Date:	Tue, 14 Oct 2014 13:12:26 -0500
From:	Michael j Theall <>
To:	Seth Forshee <>
Cc:	"Eric W. Biederman" <>,,,, Miklos Szeredi <>,
	"Serge H. Hallyn" <>
Subject: Re: [fuse-devel] [PATCH v4 4/5] fuse: Support privileged xattrs only	with a
 mount option

Seth Forshee <> wrote on 10/14/2014 09:25:55 AM:

> From: Seth Forshee <>
> To: Miklos Szeredi <>
> Cc:, "Serge H. Hallyn" 
> <>,, Seth 
> Forshee <>, "Eric W. Biederman" 
> <>,
> Date: 10/14/2014 09:27 AM
> Subject: [fuse-devel] [PATCH v4 4/5] fuse: Support privileged xattrs
> only with a mount option
> Allowing unprivileged users to provide arbitrary xattrs via fuse
> mounts bypasses the normal restrictions on setting xattrs. Such
> mounts should be restricted to reading and writing xattrs in the
> user.* namespace.

Can you explain how the normal restrictions on setting xattrs are 
My filesystem still needs security.* and system.*, and it looks like
xattr_permission already prevents non-privileged users from accessing

> It's difficult though to tell whether a mount is being performed
> on behalf of an unprivileged user since fuse mounts are ususally
> done via a suid root helper. Thus a new mount option,
> privileged_xattrs, is added to indicated that xattrs from other
> namespaces are allowed. This option can only be supplied by
> system-wide root; supplying the option as an unprivileged user
> will cause the mount to fail.

I can't say I'm convinced that this is the right direction to head.

Michael Theall

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