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From: Andy Lutomirski <luto@kernel.org>
Date: Thu, 25 Mar 2021 21:58:54 -0700
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Subject: Re: [PATCH v7 5/6] x86/signal: Detect and prevent an alternate signal
 stack overflow
To: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
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I forgot to mention why I cc'd all you fine Xen folk:

On Thu, Mar 25, 2021 at 11:13 AM Andy Lutomirski <luto@kernel.org> wrote:

>
> >         } else if (IS_ENABLED(CONFIG_X86_32) &&
> >                    !onsigstack &&
> >                    regs->ss != __USER_DS &&

This bit here seems really dubious on Xen PV.  Honestly it seems
dubious everywhere, but especially on Xen PV.

--Andy