- fix MsiSummaryInfoGetProperty to return ERROR_MORE_DATA if the
  buffer is too small (based on a patch by Aric Stewart)
- add a test case to show correct behaviour

dlls/msi/suminfo.c

diff --git a/dlls/msi/suminfo.c b/dlls/msi/suminfo.c
index 46c1e5b..a59863a 100644
--- a/dlls/msi/suminfo.c
+++ b/dlls/msi/suminfo.c
@@ -544,6 +544,7 @@
 {
     MSISUMMARYINFO *si;
     PROPVARIANT *prop;
+    UINT ret = ERROR_SUCCESS;
 
     TRACE("%ld %d %p %p %p %p %p\n", handle, uiProperty, puiDataType,
           piValue, pftValue, str, pcchValueBuf);
@@ -583,6 +584,8 @@
                 if( str->str.a )
                     lstrcpynA(str->str.a, prop->u.pszVal, *pcchValueBuf );
             }
+            if (len >= *pcchValueBuf)
+                ret = ERROR_MORE_DATA;
             *pcchValueBuf = len;
         }
         break;
@@ -597,7 +600,7 @@
         break;
     }
     msiobj_release( &si->hdr );
-    return ERROR_SUCCESS;
+    return ret;
 }
 
 UINT WINAPI MsiSummaryInfoGetPropertyA(

dlls/msi/tests/suminfo.c

diff --git a/dlls/msi/tests/suminfo.c b/dlls/msi/tests/suminfo.c
index b0f81b0..80c050a 100644
--- a/dlls/msi/tests/suminfo.c
+++ b/dlls/msi/tests/suminfo.c
@@ -67,7 +67,7 @@
     const char *msifile = "winetest.msi";
     MSIHANDLE hdb = 0, hsuminfo;
     UINT r, count, type;
-    DWORD dwcount;
+    DWORD sz;
     INT val;
     FILETIME ft;
     char buf[0x10];
@@ -112,11 +112,11 @@
 
     buf[0]='x';
     buf[1]=0;
-    dwcount = 0x10;
-    r = MsiSummaryInfoGetProperty(hsuminfo, PID_REVNUMBER, &type, &val, NULL, buf, &dwcount);
+    sz = 0x10;
+    r = MsiSummaryInfoGetProperty(hsuminfo, PID_REVNUMBER, &type, &val, NULL, buf, &sz);
     ok(r == ERROR_SUCCESS, "getpropcount failed\n");
     ok(buf[0]=='x', "cleared buffer\n");
-    ok(dwcount == 0x10, "count wasn't zero\n");
+    ok(sz == 0x10, "count wasn't zero\n");
     ok(type == VT_EMPTY, "should be empty\n");
 
     r = MsiSummaryInfoSetProperty(hsuminfo, PID_TITLE, VT_LPSTR, 0, NULL, "Mike");
@@ -177,6 +177,22 @@
     r = MsiSummaryInfoSetProperty(hsuminfo, PID_TITLE, VT_LPSTR, 0, NULL, "Mike");
     ok(r == ERROR_SUCCESS, "MsiSummaryInfoSetProperty failed\n");
 
+    sz = 2;
+    strcpy(buf,"x");
+    r = MsiSummaryInfoGetProperty(hsuminfo, PID_TITLE, &type, NULL, NULL, buf, &sz );
+    ok(r == ERROR_MORE_DATA, "MsiSummaryInfoSetProperty failed\n");
+    ok(sz == 4, "count was wrong\n");
+    ok(type == VT_LPSTR, "type was wrong\n");
+    ok(!strcmp(buf,"M"), "buffer was wrong\n");
+
+    sz = 4;
+    strcpy(buf,"x");
+    r = MsiSummaryInfoGetProperty(hsuminfo, PID_TITLE, &type, NULL, NULL, buf, &sz );
+    ok(r == ERROR_MORE_DATA, "MsiSummaryInfoSetProperty failed\n");
+    ok(sz == 4, "count was wrong\n");
+    ok(type == VT_LPSTR, "type was wrong\n");
+    ok(!strcmp(buf,"Mik"), "buffer was wrong\n");
+
     r = MsiSummaryInfoSetProperty(hsuminfo, PID_TITLE, VT_LPSTR, 0, NULL, "JungAh");
     ok(r == ERROR_SUCCESS, "MsiSummaryInfoSetProperty failed\n");