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Date: Fri, 27 Oct 2017 14:46:58 -0700
From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@suse.de>,
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        Paolo Bonzini <pbonzini@redhat.com>, Liang Z Li <liang.z.li@intel.com>,
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        X86 ML <x86@kernel.org>, "Neri, Ricardo" <ricardo.neri@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>, Tony Luck <tony.luck@intel.com>
Subject: Re: [PATCH v9 25/29] x86/umip: Force a page fault when unable to
 copy emulated result to user
Message-ID: <20171027214658.GA14203@voyager>
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On Thu, Oct 26, 2017 at 12:59:55AM -0700, Andy Lutomirski wrote:
> On Tue, Oct 3, 2017 at 8:54 PM, Ricardo Neri
> <ricardo.neri-calderon@linux.intel.com> wrote:
> > fixup_umip_exception() will be called from do_general_protection(). If the
> > former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV.
> > However, when emulation is successful but the emulated result cannot be
> > copied to user space memory, it is more accurate to issue a SIGSEGV with
> > SEGV_MAPERR with the offending address. A new function, inspired in
> > force_sig_info_fault(), is introduced to model the page fault.
> 
> This code is slightly buggy (with, for example, PKRU, although the
> chance that anyone ever notices is about nil).  For an alternative
> approach, see current->thread.sig_on_uaccess_err, used in
> arch/x86/entry/vsyscall/vsyscall_64.c.  But I'm fine with this patch
> as is, too.

Thanks Andy, I will study the alternative you mention. Since you are OK
with this patch, I will submit v10 of this series to allow the review
of the series to continue.

BR,
Ricardo