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From: Philipp Hahn <hahn@univention.de>
To: George Dunlap <george.dunlap@citrix.com>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Keir Fraser" <keir.fraser@citrix.com>,
	"Nico Stöckigt" <Stoeckigt@univention.de>,
	"xen-devel@lists.xen.org" <Xen-devel@lists.xen.org>
Subject: Re: [xen-] SIGSEGV libxc/xc_save_domain.c: p2m_size >> configured_ram_size
Date: Mon, 13 Jun 2016 13:14:28 +0200	[thread overview]
Message-ID: <575E9594.9010708@univention.de> (raw)
In-Reply-To: <CAFLBxZbfhrZY=RSZ0NEwLu2vvAfKNtvS0=BgHFWuYAEmnA+O4g@mail.gmail.com>

Hello Georg,

first of all thank you for answering.

Am 13.06.2016 um 12:15 schrieb George Dunlap:
> On Fri, Jun 10, 2016 at 4:22 PM, Philipp Hahn <hahn@univention.de> wrote:
>> while trying to live migrate some VMs from an xen- host "xc_save"
>> crashes with a segmentation fault in tools/libxc/xc_domain_save.c:1141
>>>         /*
>>>          * Quick belt and braces sanity check.
>>>          */
>>>         for ( i = 0; i < dinfo->p2m_size; i++ )
>>>         {
>>>             mfn = pfn_to_mfn(i);
>>>             if( (mfn != INVALID_P2M_ENTRY) && (mfn_to_pfn(mfn) != i) )
>>                                                  ^^^^^^^^^^^^^^^
>> due to a de-reference through
>>> #define pfn_to_mfn(_pfn)                                            \
>>>   ((xen_pfn_t) ((dinfo->guest_width==8)                               \
>>>                 ? (((uint64_t *)ctx->live_p2m)[(_pfn)])                  \
>>>                 : ((((uint32_t *)ctx->live_p2m)[(_pfn)]) == 0xffffffffU  \
>>>                    ? (-1UL) : (((uint32_t *)ctx->live_p2m)[(_pfn)]))))
> Given that 4.1 is long out of support, we won't be making a proper fix
> in-tree (since it will never be released).

I know that 4.1 is EOL.
I'm aware of Ubuntu still having xen-4.1 in one of their LTS versions
(Precise) and its also in Debian-oldstable, which a lot people (us
included) still use. I would prefer to update, but I can for reasons
outside my direct control.

I'm already working with Stefan Bader from Canonical to backport most of
the XSAs to 4.1, so there already exists a "better" version outside of
the official Xen repositories.

> So what kind of resolution
> would be the most help to you?  A patch you can apply locally to allow
> the save/restore to work?

A patch is okay. I've already fixed a lot other bugs in xen-4.1 by
patching the last release, so compiling my own version is no problem for me.


Xen-devel mailing list

  reply	other threads:[~2016-06-13 11:14 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-10 15:22 [xen-] SIGSEGV libxc/xc_save_domain.c: p2m_size >> configured_ram_size Philipp Hahn
2016-06-13 10:15 ` George Dunlap
2016-06-13 11:14   ` Philipp Hahn [this message]
2016-06-17  9:31     ` Xen 4.1 maintenance? (Was Re: [xen-] SIGSEGV libxc/xc_save_domain.c: p2m_size >> configured_ram_size) George Dunlap
2016-06-29  9:46       ` Stefan Bader

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