[Xen-changelog] [xen-4.2-testing] x86: fix hypercall continuation cancellation in XENMAPSPACE_gmfn_range compat wrapper

[Xen patchbot-4.2-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1354788476 -3600
# Node ID 594b333b211d8926270e65b6dc962d1d26a6e73b
# Parent  6efa959326cc1eba19840d9caa1af1a12c3afe72
x86: fix hypercall continuation cancellation in XENMAPSPACE_gmfn_range compat 
wrapper

When no continuation was established, there must also not be an attempt
to cancel it - hypercall_cancel_continuation(), in the non-HVM, non-
multicall case, adjusts the guest mode return address in a way assuming
that an earlier call hypercall_create_continuation() took place.

Once touching this code, also restructure it slightly to improve
readability and switch to using the more relaxed copy function (copying
from the same guest memory already validated the virtual address
range).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
xen-unstable changeset: 26195:7670eabcbafc
xen-unstable date: Wed Nov 28 09:02:26 UTC 2012
---


diff -r 6efa959326cc -r 594b333b211d xen/arch/x86/x86_64/compat/mm.c
--- a/xen/arch/x86/x86_64/compat/mm.c   Thu Dec 06 11:01:46 2012 +0100
+++ b/xen/arch/x86/x86_64/compat/mm.c   Thu Dec 06 11:07:56 2012 +0100
@@ -66,21 +66,20 @@ int compat_arch_memory_op(int op, XEN_GU
         XLAT_add_to_physmap(nat, &cmp);
         rc = arch_memory_op(op, guest_handle_from_ptr(nat, void));
 
-        if ( cmp.space == XENMAPSPACE_gmfn_range )
+        if ( !rc || cmp.space != XENMAPSPACE_gmfn_range )
+            break;
+
+        XLAT_add_to_physmap(&cmp, nat);
+        if ( __copy_to_guest(arg, &cmp, 1) )
         {
-            if ( rc )
-            {
-                XLAT_add_to_physmap(&cmp, nat);
-                if ( copy_to_guest(arg, &cmp, 1) )
-                {
-                    hypercall_cancel_continuation();
-                    return -EFAULT;
-                }
-            }
             if ( rc == __HYPERVISOR_memory_op )
-                hypercall_xlat_continuation(NULL, 0x2, nat, arg);
+                hypercall_cancel_continuation();
+            return -EFAULT;
         }
 
+        if ( rc == __HYPERVISOR_memory_op )
+            hypercall_xlat_continuation(NULL, 0x2, nat, arg);
+
         break;
     }
 

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog