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From: ebiederm-aS9lmoZGLiVWk0Htik3J/ (Eric W. Biederman)
To: Andrei Vagin <>
Cc: Andrei Vagin <>,,
	Linux Containers
	Alexander Viro
Subject: Re: [PATCH] fs: add an ioctl to get an owning userns for a superblock
Date: Wed, 10 May 2017 20:24:00 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (Andrei Vagin's message of "Wed, 10 May 2017 17:15:27 -0700")

Andrei Vagin <> writes:

> On Tue, May 09, 2017 at 07:34:00PM -0500, Eric W. Biederman wrote:
>> Andrei Vagin <> writes:
>> > The introduced ioctl returns a file descriptor that refers to a owning
>> > user namespace for a superblock which is associated with a target file
>> > descriptor.
>> >
>> > EPERM is returned if the current process doesn't have CAP_SYS_ADMIN in
>> > the returned user namespace.
>> >
>> > This information is required to dump and restore mount namespaces. We
>> > need to know to which user namespace a superblock is belonged to.
>> >
>> > We already have the SIOCGSKNS ioctl for sockets to get a network
>> > namespace, so it looks reasonable to use the same interface for
>> > superblocks too.
>> >
>> > This functionality can be useful for users in order to understand
>> > a running system.
>> This will probably work.  And the capability check eases any concerns
>> I might have that this would be a trivial information leak.
>> That said can we hold off just a little bit.  If open_fs work actually
>> turns into a real interface that would seem to be the perfect place
>> to stick this functionality.
> Sure, we can. Do you know any place where to read more information about
> open_fs? I think I have heared a few times about this idea, but it would be
> good to get more details.

Look for David Howells <> recent patches on lkml he
has implemented an initial rfc for it.


      parent reply	other threads:[~2017-05-11  1:24 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-09 23:19 Andrei Vagin
     [not found] ` <>
2017-05-10  0:34   ` Eric W. Biederman
     [not found]     ` <87k25psg7b.fsf-aS9lmoZGLiVWk0Htik3J/>
2017-05-11  0:15       ` Andrei Vagin
     [not found]         ` <>
2017-05-11  1:24           ` Eric W. Biederman [this message]

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