[Pkg-xen-devel] Bug#900746: xen toolstack xl causes a Segmentation fault on create domu

[Hans van Kranenburg]

Hi,

On 06/28/2018 09:58 AM, Damian Pietras wrote:
> I've also hit it on one of my boxes with
> 4.8.3+xsa267+shim4.10.1+xsa267-1+deb9u8
> 
> This is related to too small stack size set for threads in XEN utils
> which explicitly set it to use 16KB. Similar issue is reported here for
> NTP: https://bugzilla.redhat.com/show_bug.cgi?id=1564527
> 
> I've recompilled the package with the attached patch to increase the
> stack size from 16KB to 32KB and it works.

Thanks for doing "bug triaging"!

> Technical details:
> 
> The issue appears with modern CPU that support AVX-512 instruction set,
> in my case it's Intel(R) Xeon(R) Gold 6148. More details are in this
> bug report against glibc: https://bugzilla.redhat.com/show_bug.cgi?id=1
> 527887#c18
> 
> There was a post on xen-users acknowledging the bug that says it's
> fixed in XEN 4.11: https://lists.xenproject.org/archives/html/xen-users
> /2018-05/msg00034.html

Following that post and what happened afterwards leads me to upstream
commit 448c03b3cb "tools/xenstore: try to get minimum thread stack size
for watch thread", which seems to solve this problem without hardcoding
some size.

Maybe this should be a nice candidate for upstream backport to stable
branches, since users are buying newer hardware and otherwise cannot use
Debian Stable without recompiling their Xen packages?

Ian?

Thanks,
Hans