linux-kernel - Re: [PATCH 0/5] userns: bump idmap limits, fixes & tweaks

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Message-ID: <CAPP7u0WDVv0pAAFEuzL2c9Y-wVg0xG36jyH-eok=GV-r6UewZg@mail.gmail.com>
Date:   Wed, 1 Nov 2017 11:51:17 +0100
From:   Christian Brauner <christian.brauner@...onical.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Serge Hallyn <serge@...lyn.com>,
        Tycho Andersen <tycho@...ho.ws>,
        Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH 0/5] userns: bump idmap limits, fixes & tweaks

On Tue, Oct 31, 2017 at 06:46:32PM -0500, Eric W. Biederman wrote:
>
> Christian I have looked through your code and I have found one real
> issue and of things I want to twak

Cool, thanks for taking a close look Eric.

>
> The real issue is reading nr_extents multiple times when reading a map.
> That can introduce races that will allow walking past the end of the
> array, if the first read is 0 but the second read is > 5.
>
> I have also found a couple of tweaks that look like they are worth
> implementing.

Yeah, I saw that you unified some of the functions. I was thinking about this
but wanted to keep the cases distinct even with some amount of code duplication.
But it seems very much worth it from a maintenance perspective. Thanks!

>
> As all of these are very small and very straight forward I have
> tested these and applied them all to my for-next branch

Thanks for the fixes Eric. Really appreciated. If you're too swamped for stuff
like that I'm obviously happy to do such trivial fixes myself. :)

Christian

>
>
> Eric W. Biederman (5):
>       userns: Don't special case a count of 0
>       userns: Simplify the user and group mapping functions
>       userns: Don't read extents twice in m_start
>       userns: Make map_id_down a wrapper for map_id_range_down
>       userns: Simplify insert_extent
>
>  kernel/user_namespace.c | 159 ++++++++++++++++--------------------------------
>  1 file changed, 51 insertions(+), 108 deletions(-)
>
>
>
>