Re: [PATCH] Fix cpumap setting before passing to XEN

[Zhenzhong Duan <zhenzhong.duan@oracle.com>]

On 2016/4/25 21:26, Ian Jackson wrote:
> Konrad Rzeszutek Wilk writes ("Re: [Xen-devel] [PATCH] Fix cpumap setting before passing to XEN"):
>> On Wed, Apr 20, 2016 at 03:33:13PM +0100, Wei Liu wrote:
>>> In principle I think having python binding and xl/libxl behave more or less
>>> the same is the right direction. I'm a bit nervous about the change of
>>> behaviour on the other hand.
>>>
>>> Let's wait for a few more days to see if other people have any comment on
>>> this.
>> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> ?
> Does this bug report mean that `xm vcpu-pin ... all' has never
> worked properly ?  Can that really be the case ?
Xen 4.3 doesn't work, Xen 3.4 works.
I have no Xen 4.4 around to test that, but checked code, it will not.
Then I found below commit involved.

commit 41abbadef60e5fccdfd688579dd458f7f7887cf5
Author: Ian Jackson <ian.jackson@eu.citrix.com>
Date:   Wed May 29 15:48:11 2013 +0100

     libxc: limit cpu values when setting vcpu affinity

     When support for pinning more than 64 cpus was added, check for cpu
     out-of-range values was removed. This can lead to subsequent
     out-of-bounds cpumap array accesses in case the cpu number is higher
     than the actual count.

     This patch returns the check.

     This is CVE-2013-2072 / XSA-56

     Signed-off-by: Petr Matousek <pmatouse@redhat.com>
>
> Also, xm exists in Xen 4.4 and earlier, only.  Xen 4.4 is no longer
> supported upstream, so we would not apply this patch to Xen 4.4.  So
> whatever we do, this is not going to fix any bug in `xm vcpu-pin' in
> 4.4.
The only impact is upper layer or the user need to pass a correct cpumap 
param not beyond the real cpu map to avoid the error.
But I am not clear if python binding is still used or will be removed 
just as Xend.
>
> This doesn't necessarily mean that I object to changing the behaviour
> of the python xc module in still-supported Xen releases.  But I'm not
> sure the reasoning behind the behaviour of the libxl bitmap functions
> applies to the Python interface.
>
> Zhenzhong Duan, are you using an out-of-tree copy of xm and xend ?
I am using xen-4.3.0-55.el6.47.33 which is Xen 4.3 variant

thanks
zduan

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