From: David Gibson <david@gibson.dropbear.id.au>
To: passt-dev@passt.top
Subject: Re: [PATCH v2 04/10] Safer handling if we can't open /proc/self/uid_map
Date: Sat, 10 Sep 2022 17:23:25 +1000 [thread overview]
Message-ID: <Yxw7bVAFGeBwNV+L@yekko> (raw)
In-Reply-To: <20220909163352.50b566ab@elisabeth>
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On Fri, Sep 09, 2022 at 04:33:52PM +0200, Stefano Brivio wrote:
> On Thu, 8 Sep 2022 13:59:01 +1000
> David Gibson <david(a)gibson.dropbear.id.au> wrote:
>
> > passt is allowed to run as "root" (UID 0) in a user namespace, but notas
> > real root in the init namespace. We read /proc/self/uid_map to determine
> > if we're in the init namespace or not.
> >
> > If we're unable to open /proc/self/uid_map we assume we're ok and continue
> > running as UID 0. This seems unwise: AFAIK the only instance in which
> > uid_map won't be available is if we're running on a kernel which doesn't
> > support user namespaces, in which case we won't be able to sandbox
> > ourselves as we want and fail anyway.
>
> Well, if user namespaces are not supported and the UID is 0, then we're
> actually running as root, so we should quit anyway.
Right, that's kind of the whole point of this patch, but it's a bit
obscured in the wording here because I realized we'd actually fail
later anyway.
> > If there are other circumstances
> > where it can't be opened it seems marginally more likely that we *are*
> > in the init namespace.
>
> That could also happen if procfs is not mounted, but I'm not sure what
> would work then.
True. I'll reword the commit message to make both points clearer.
> > Therefore, fail with an error in this case, instead of carrying on.
>
> Yes, absolutely.
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2022-09-10 7:23 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-08 3:58 [PATCH v2 00/10] Clean up handling of userns David Gibson
2022-09-08 3:58 ` [PATCH v2 01/10] Don't store UID & GID persistently in the context structure David Gibson
2022-09-08 3:58 ` [PATCH v2 02/10] Split checking for root from dropping root privilege David Gibson
2022-09-09 14:33 ` Stefano Brivio
2022-09-10 7:09 ` David Gibson
2022-09-08 3:59 ` [PATCH v2 03/10] Consolidate determination of UID/GID to run as David Gibson
2022-09-09 14:33 ` Stefano Brivio
2022-09-10 7:15 ` David Gibson
2022-09-10 20:43 ` Stefano Brivio
2022-09-12 9:53 ` David Gibson
2022-09-13 3:49 ` Stefano Brivio
2022-09-13 5:20 ` David Gibson
2022-09-08 3:59 ` [PATCH v2 04/10] Safer handling if we can't open /proc/self/uid_map David Gibson
2022-09-09 14:33 ` Stefano Brivio
2022-09-10 7:23 ` David Gibson [this message]
2022-09-08 3:59 ` [PATCH v2 05/10] Move self-isolation code into a separate file David Gibson
2022-09-09 14:33 ` Stefano Brivio
2022-09-10 7:23 ` David Gibson
2022-09-10 20:43 ` Stefano Brivio
2022-09-08 3:59 ` [PATCH v2 06/10] Consolidate validation of pasta namespace options David Gibson
2022-09-08 3:59 ` [PATCH v2 07/10] Clean up and rename conf_ns_open() David Gibson
2022-09-08 3:59 ` [PATCH v2 08/10] Correctly handle --netns-only in pasta_start_ns() David Gibson
2022-09-09 14:34 ` Stefano Brivio
2022-09-10 7:25 ` David Gibson
2022-09-11 8:26 ` David Gibson
2022-09-13 3:50 ` Stefano Brivio
2022-09-08 3:59 ` [PATCH v2 09/10] Handle userns isolation and dropping root at the same time David Gibson
2022-09-08 3:59 ` [PATCH v2 10/10] Allow --userns when pasta spawns a command David Gibson
2022-09-09 14:34 ` Stefano Brivio
2022-09-10 7:29 ` David Gibson
2022-09-10 20:42 ` Stefano Brivio
2022-09-09 14:36 ` [PATCH v2 00/10] Clean up handling of userns Stefano Brivio
2022-09-10 7:30 ` David Gibson
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