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

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
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> ?
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@xxxxxxxxxxxxx>
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@xxxxxxxxxx>

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
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


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