Re: [libvirt] [RFC PATCH 2/2] LXC: Create ro overlay mounts only if we're not within a user namespace

Am 01.07.2013 13:22, schrieb Daniel P. Berrange: > On Mon, Jul 01, 2013 at 01:05:23PM +0200, Richard Weinberger wrote: >> Am 01.07.2013 12:33, schrieb Daniel P. Berrange: >>> On Mon, Jul 01, 2013 at 08:29:14AM +0200, Richard Weinberger wrote: >>>> Any ideas what's going on here? >>> >>> No, it is very odd. It smells like a kernel issue to me. What >>> version are you running ? >> >> I see this issue on all kernels. >> Currently I'm using vanilla v3.9.x and v3.10. >> >>> I've also tried running the demo programs shown on the LWN.net >>> article >>> >>> https://lwn.net/Articles/532593/ >>> >>> and they don't operate in the way described by the article - the demo >>> programs continue to ru as 'nfsnobody' even after the mappings are >>> setup. >>> >>> I'm just using the Fedora 3.9.4-303 kernel, rebuilt with userns enabled >>> in KConfig. I'm wondering if there is still stuff missing in 3.9.x >>> that prevents this from working properly, or if the kernel behaviour >>> changed after those LWN articles were written. >> >> To me it looks like the capability system behaves odd. >> The mappings in /proc are fine as long I do not call capng_updatev(). >> Also calling capng_updatev() with parameters that do not change the current cap set >> triggers the odd behavior too. >> >> So we see two (related?) issues: >> 1. If we try updating the capabilities of pid1 /proc/1/ has unmapped files till we exec(). >> 2. Dropping capabilities does not work we always gain a fresh and full capability set. >> >> BTW: I'm sure the issues are not caused by Gau Feng's userns patches. > > Yeah, I've reproduced this problem with standalone code outside of > libvirt. > > Take the attached code and run -ENOATTACHMENT :-(