Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup

[H. Peter Anvin]

On April 11, 2016 1:12:22 PM PDT, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>On Sat, Apr 9, 2016 at 6:27 PM, Linus Torvalds
><torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>>
>> On Apr 9, 2016 5:45 PM, "Andy Lutomirski" <luto@xxxxxxxxxxxxxx>
>wrote:
>>>
>>>
>>> What we *do* want to do, though, is to prevent the following:
>>
>> I don't see the point. Why do you bring up this insane scenario that
>nobody
>> can possibly care about?
>>
>> So you actually have any reason to believe somebody does that?
>>
>> I already asked about that earlier, and the silence was deafening.
>
>I have no idea, but I'm generally uncomfortable with magical things
>that bypass normal security policy.
>
>That being said, here's an idea for fixing this, at least in the long
>run.  Add a new devpts mount option "no_ptmx_redirect" that turns off
>this behavior for the super in question.  That is, opening /dev/ptmx
>if "pts/ptmx" points to something with no_ptmx_redirect set will fail.
>Distros shipping new kernels could be encouraged to (finally!) make
>/dev/ptmx a symlink and set this option.
>
>We just might be able to get away with spelling that option
>"newinstance".

What about the idea of making the bind mount automatic?
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