[Devel] Re: [PATCHSET] 2.6.20-rc4-mm1-lxc2

[Dmitry Mishin]

On Wednesday 17 January 2007 02:48, Daniel Lezcano wrote:
> Cedric Le Goater wrote:
> > All,
> > 
> > We've been gathering and porting patches related to namespaces in
> > a lxc patchset for a while now. Mostly working on the network
> > namespace which will require some extra work to be usable. 
> > 
> >  * It's available here :
> > 
> > 	http://www.sr71.net/patches/2.6.20/2.6.20-rc4-mm1-lxc2/
> > 
> > * Caveats :
> > 
> >   namespace syscalls are still under construction.
> > 
> >   network namespace is broken : 
> > 
> >   . the nsproxy backpointer in net_ns is flaky. 
> >   . the push_net_ns() and pop_net_ns() can be called under 
> >     irq and are using current. this seems inappropriate.
> >   . there is a race on ->nsproxy between push_net_ns() and 
> >     exit_task_namespaces()
> 
> Hi Dmitry,
> 
> we are experiencing NULL address access when using the nsproxy in 
> push_net_ns function without any unshare.
> 
> It appears the exit_task_namespace function sets current->nsproxy to 
> NULL and we are interrupted by an incoming packet. The netif_receive_skb 
> does push_net_ns(dev->net_ns). The push_net_ns function retrieves the 
> current->nsproxy to use it. But it was previously set to NULL by the 
> exit_task_namespace function.
> 
> The bug can be reproduced with the following command launched from 
> another host.
> 
> while $(true); do ssh myaddress ls > /dev/null && echo -n .; done
> 
> After a time (between 1 second - 3 minutes), the kernel panics.
> 
> I think this will be very hard to fix and perhaps we should redesign 
> some part. Instead of using nsproxy swapping, perhaps we should pass 
> net_ns as parameter to functions, but that will breaks a lot of API. 
I've redesigned this already to use per-CPU global variable, as Eric
suggests. Updated l2 networking patchset will be sent later today or tommorow.
Sorry for the latency, there were very long holidays here :)


-- 
Thanks,
Dmitry.
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