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From: "Michael Kerrisk (man-pages)" <>
To: "Eric W. Biederman" <>
Cc:, "Serge E. Hallyn" <>,,,, Andrey Vagin <>,
	James Bottomley <>,
	"W. Trevor King" <>,
	Alexander Viro <>,
	Jonathan Corbet <>,
	Andrei Vagin <>
Subject: Re: [PATCH 0/2] Add further ioctl() operations for namespace discovery
Date: Thu, 22 Dec 2016 08:20:33 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Eric,

On 12/22/2016 01:27 AM, Eric W. Biederman wrote:
> "Michael Kerrisk (man-pages)" <> writes:
>> Hi Eric,
>> On 12/21/2016 01:17 AM, Eric W. Biederman wrote:
>>> "Michael Kerrisk (man-pages)" <> writes:
>>>> Hi Eric,
>>>> On 12/20/2016 09:22 PM, Eric W. Biederman wrote:
>>>>> "Michael Kerrisk (man-pages)" <> writes:
>>>>>> Hello Eric,
>>>>>> On 12/19/2016 11:53 PM, Eric W. Biederman wrote:
>>>>>>> "Michael Kerrisk (man-pages)" <> writes:
>>> Now the question becomes who are the users of this?  Because it just
>>> occurred to me that we now have an interesting complication.  Userspace
>>> extending the meaning of the capability bits, and using to protect
>>> additional things.  Ugh.  That could be a maintenance problem of another
>>> flavor.  Definitely not my favorite.
>> I don't follow you here. Could you say some more about what you mean?
> I have seen user space userspace do thing such as extend CAP_SYS_REBOOT
> to things such as permission to invoke "shutdown -r now".  Which
> depending on what a clean reboot entails could be greately increasing
> the scope of CAP_SYS_REBOOT.
> I am concerned for that and similar situations that userspace
> applications could lead us into situation that one wrong decision could
> wind up being an unfixable mistake because fixing the mistake would
> break userspsace.


>>> So why are we asking the questions about what permissions a process has?
>> My main interest here is monitoring/discovery/debugging on a running
>> NS_GET_NSTYPE provide most of what I'd like to see. Being able to ask
>> "does this process have permissions in that namespace?" would be nice 
>> to have in terms of understanding/debugging a system.
> If we are just looking at explanations then I seem to have been
> over-engineering things.  So let's just aim at the two ioctls.
> Or at least the information in those ioctls.


> With at least a comment on the ioctl returning the OWNER_UID that
> describes why it is not a problem to if the owners uid is something like
> ((uid_t)-3).  Which overlaps with the space for error return codes.
> I don't know if we are fine or not, but that review comment definitely
> deserves some consideration.

See my reply just sent to Andrei. We should instead then just return 
the UID via a buffer pointed to by the ioctl() argument:

ioctl(fd, NS_GET_OWNER_UID, &uid);



Michael Kerrisk
Linux man-pages maintainer;
Linux/UNIX System Programming Training:

  reply	other threads:[~2016-12-22  7:20 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-19 14:38 [PATCH 0/2] Add further ioctl() operations for namespace discovery Michael Kerrisk (man-pages)
2016-12-19 22:53 ` Eric W. Biederman
2016-12-20 15:35   ` Michael Kerrisk (man-pages)
2016-12-20 20:22     ` Eric W. Biederman
2016-12-20 20:55       ` Michael Kerrisk (man-pages)
2016-12-21  0:17         ` Eric W. Biederman
2016-12-21  9:53           ` Michael Kerrisk (man-pages)
2016-12-22  0:27             ` Eric W. Biederman
2016-12-22  7:20               ` Michael Kerrisk (man-pages) [this message]
2016-12-22 10:28                 ` Eric W. Biederman

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