Patch "x86/xen: allow userspace access during hypercalls" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

x86/xen: allow userspace access during hypercalls

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-xen-allow-userspace-access-during-hypercalls.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
<[email protected]>
Date: Mon, 26 Jun 2017 14:49:46 +0200
Subject: x86/xen: allow userspace access during hypercalls
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From: Marek Marczykowski-Górecki <[email protected]>

commit c54590cac51db8ab5fd30156bdaba34af915e629 upstream.

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.

The same applies to HYPERVISOR_dm_op, where additionally privcmd driver carefully verify buffer addresses.

---
 arch/x86/include/asm/xen/hypercall.h |    3 +++
 1 file changed, 3 insertions(+)

@@ -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;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/x86-xen-allow-userspace-access-during-hypercalls.patch