Re: [CFT][PATCH 6/7] userns: Add a knob to disable setgroups on a per user namespace basis

From: Eric W. Biederman
Date: Tue Dec 09 2014 - 14:34:14 EST

ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes:

> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes:
>> This text was actually my suggested comment text.
> Now I see.
>> If you put smp_rmb() in this function with a comment like that, then I
>> think it will all make sense and be obviously correct (even with most
>> of the other barriers removed).
> Right.
> Given that we have to be careful when using these things anyway what
> I was hoping to achieve with the barriers appears impossible, and
> confusing so I will see about just adding barriers where we need them
> for real. Sigh.

Doh. The code has been entirely too clever.

There are no need for atomics or other cleverness, I just need to
generalize id_map_mutex. I knew that had to be a trivially correct
way of handling this mess.

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