[Xen-changelog] Fix SETMAXMEM dom0_op with proper locking.

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 1d8b3c85121de189882dee5e2dae54697cf52499
# Parent  5102cd121a360fd38e9792356a62f187599ef9ba
Fix SETMAXMEM dom0_op with proper locking.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 5102cd121a36 -r 1d8b3c85121d xen/common/dom0_ops.c
--- a/xen/common/dom0_ops.c     Sat Apr 15 08:47:55 2006
+++ b/xen/common/dom0_ops.c     Sat Apr 15 08:52:32 2006
@@ -581,27 +581,31 @@
     case DOM0_SETDOMAINMAXMEM:
     {
         struct domain *d; 
+        unsigned long new_max;
+
         ret = -ESRCH;
         d = find_domain_by_id(op->u.setdomainmaxmem.domain);
-        if ( d != NULL )
-        {
-            unsigned long new_max;
-            new_max = op->u.setdomainmaxmem.max_memkb >> (PAGE_SHIFT-10);
-            if (new_max < d->tot_pages) 
-                ret = -EINVAL;
-            else 
-            {  
-                d->max_pages = new_max;
-                ret = 0;
-            }
-            put_domain(d);
-        }
+        if ( d == NULL )
+            break;
+
+        ret = -EINVAL;
+        new_max = op->u.setdomainmaxmem.max_memkb >> (PAGE_SHIFT-10);
+
+        spin_lock(&d->page_alloc_lock);
+        if ( new_max >= d->tot_pages )
+        {
+            d->max_pages = new_max;
+            ret = 0;
+        }
+        spin_unlock(&d->page_alloc_lock);
+
+        put_domain(d);
     }
     break;
 
     case DOM0_SETDOMAINHANDLE:
     {
-        struct domain *d; 
+        struct domain *d;
         ret = -ESRCH;
         d = find_domain_by_id(op->u.setdomainhandle.domain);
         if ( d != NULL )

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