linux-kernel - Re: [PATCH] x86/xen: allow userspace access during hypercalls

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Message-ID: <6f8113d8-10a2-b23f-16c1-8b97b2fba0bb@suse.com>
Date:   Mon, 26 Jun 2017 14:05:48 +0200
From:   Juergen Groß <jgross@...e.com>
To:     Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, xen-devel@...ts.xenproject.org
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] x86/xen: allow userspace access during hypercalls

On 06/23/2017 02:47 PM, Marek Marczykowski-Górecki wrote:
> Userspace application can do a hypercall through /dev/xen/privcmd, and
> some for some hypercalls argument is a pointers to user-provided
> structure. When SMAP is supported and enabled, hypervisor can't access.
> So, lets allow it.

What about HYPERVISOR_dm_op?


Juergen

> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> ---
>   arch/x86/include/asm/xen/hypercall.h | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
> index f6d20f6..a1d2c5d 100644
> --- a/arch/x86/include/asm/xen/hypercall.h
> +++ b/arch/x86/include/asm/xen/hypercall.h
> @@ -43,6 +43,7 @@
>   
>   #include <asm/page.h>
>   #include <asm/pgtable.h>
> +#include <asm/smap.h>
>   
>   #include <xen/interface/xen.h>
>   #include <xen/interface/sched.h>
> @@ -214,10 +215,12 @@ privcmd_call(unsigned call,
>   	__HYPERCALL_DECLS;
>   	__HYPERCALL_5ARG(a1, a2, a3, a4, a5);
>   
> +	stac();
>   	asm volatile("call *%[call]"
>   		     : __HYPERCALL_5PARAM
>   		     : [call] "a" (&hypercall_page[call])
>   		     : __HYPERCALL_CLOBBER5);
> +	clac();
>   
>   	return (long)__res;
>   }
>