From: Jan Beulich <jbeulich@suse.com>
Date: Tue, 4 Dec 2012 18:38:14 +0000 (+0000)
Subject: xen: add missing guest address range checks to XENMEM_exchange handlers
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~7573
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=d28573565f35c4b85ca25044e162745523176392;p=xen.git

xen: add missing guest address range checks to XENMEM_exchange handlers

Ever since its existence (3.0.3 iirc) the handler for this has been
using non address range checking guest memory accessors (i.e.
the ones prefixed with two underscores) without first range
checking the accessed space (via guest_handle_okay()), allowing
a guest to access and overwrite hypervisor memory.

This is XSA-29 / CVE-2012-5513.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
---

diff --git a/xen/common/compat/memory.c b/xen/common/compat/memory.c
index 996151caed..a49f51b7fb 100644
--- a/xen/common/compat/memory.c
+++ b/xen/common/compat/memory.c
@@ -115,6 +115,12 @@ int compat_memory_op(unsigned int cmd, XEN_GUEST_HANDLE_PARAM(void) compat)
                   (cmp.xchg.out.nr_extents << cmp.xchg.out.extent_order)) )
                 return -EINVAL;
 
+            if ( !compat_handle_okay(cmp.xchg.in.extent_start,
+                                     cmp.xchg.in.nr_extents) ||
+                 !compat_handle_okay(cmp.xchg.out.extent_start,
+                                     cmp.xchg.out.nr_extents) )
+                return -EFAULT;
+
             start_extent = cmp.xchg.nr_exchanged;
             end_extent = (COMPAT_ARG_XLAT_SIZE - sizeof(*nat.xchg)) /
                          (((1U << ABS(order_delta)) + 1) *
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 83e266646d..bdb6ed8f35 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -308,6 +308,13 @@ static long memory_exchange(XEN_GUEST_HANDLE_PARAM(xen_memory_exchange_t) arg)
         goto fail_early;
     }
 
+    if ( !guest_handle_okay(exch.in.extent_start, exch.in.nr_extents) ||
+         !guest_handle_okay(exch.out.extent_start, exch.out.nr_extents) )
+    {
+        rc = -EFAULT;
+        goto fail_early;
+    }
+
     /* Only privileged guests can allocate multi-page contiguous extents. */
     if ( !multipage_allocation_permitted(current->domain,
                                          exch.in.extent_order) ||