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

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Message-Id: <1498222072-18217-1-git-send-email-marmarek@invisiblethingslab.com>
Date:   Fri, 23 Jun 2017 14:47:52 +0200
From:   Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
To:     xen-devel@...ts.xenproject.org
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, stable@...r.kernel.org
Subject: [PATCH] x86/xen: allow userspace access during hypercalls

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.

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;
 }
-- 
2.7.4