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

Am 01.07.2013 12:33, schrieb Daniel P. Berrange: > On Mon, Jul 01, 2013 at 08:29:14AM +0200, Richard Weinberger wrote: >> Am 01.07.2013 04:26, schrieb Gao feng: >>>> Well, given that we're at rc2 now & I'm still unclear about how some >>>> aspects of the userns setup is working, I'm afraid we'll have to wait >>>> until 1.1.1 for the userns LXC code to merge. I'll aim todo it next >>>> week, so that we have plenty of time for further testing before the >>>> 1.1.1 release. >>>> >>> >>> Ok, I think Richard had tested the userns support. >>> Hi Richard, can you give me your ack or tested-by? >> >> I'm still facing one userns related issue. > > [snip] > >> After creating it attach to it's console, you'll find bash as pid 1. >> And you'll find that /proc/1/ is not fully uid/gid-mapped: >> ---cut--- >> # ls -la /proc/1/ >> total 0 >> dr-xr-xr-x 8 root root 0 Jul 1 06:06 . >> dr-xr-xr-x 74 nobody nogroup 0 Jul 1 06:06 .. >> dr-xr-xr-x 2 root root 0 Jul 1 06:06 attr > > [snip] > >> 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.

Feel free to add: Acked-by: Richard Weinberger <richard(a)nod.at&gt; Tested-by: Richard Weinberger <richard(a)nod.at&gt;