[Xen-changelog] [xen-unstable] xen: fix error handling of guest_physmap_mark_populate_on_demand()

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1354646300 0
# Node ID ddf4ead1afda24f7bf3f4ebcc1f7c78061ad1055
# Parent  b406e395995fcf174475e4ca3db21a2d55e627cd
xen: fix error handling of guest_physmap_mark_populate_on_demand()

The only user of the "out" label bypasses a necessary unlock, thus
enabling the caller to lock up Xen.

Also, the function was never meant to be called by a guest for itself,
so rather than inspecting the code paths in depth for potential other
problems this might cause, and adjusting e.g. the non-guest printk()
in the above error path, just disallow the guest access to it.

Finally, the printk() (considering its potential of spamming the log,
the more that it's not using XENLOG_GUEST), is being converted to
P2M_DEBUG(), as debugging is what it apparently was added for in the
first place.

This is XSA-30 / CVE-2012-5514.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
---


diff -r b406e395995f -r ddf4ead1afda xen/arch/x86/mm/p2m-pod.c
--- a/xen/arch/x86/mm/p2m-pod.c Tue Dec 04 18:38:14 2012 +0000
+++ b/xen/arch/x86/mm/p2m-pod.c Tue Dec 04 18:38:20 2012 +0000
@@ -1117,6 +1117,9 @@ guest_physmap_mark_populate_on_demand(st
     mfn_t omfn;
     int rc = 0;
 
+    if ( !IS_PRIV_FOR(current->domain, d) )
+        return -EPERM;
+
     if ( !paging_mode_translate(d) )
         return -EINVAL;
 
@@ -1131,8 +1134,7 @@ guest_physmap_mark_populate_on_demand(st
         omfn = p2m->get_entry(p2m, gfn + i, &ot, &a, 0, NULL);
         if ( p2m_is_ram(ot) )
         {
-            printk("%s: gfn_to_mfn returned type %d!\n",
-                   __func__, ot);
+            P2M_DEBUG("gfn_to_mfn returned type %d!\n", ot);
             rc = -EBUSY;
             goto out;
         }
@@ -1156,9 +1158,9 @@ guest_physmap_mark_populate_on_demand(st
         pod_unlock(p2m);
     }
 
+out:
     gfn_unlock(p2m, gfn, order);
 
-out:
     return rc;
 }
 

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