Only exact buffer size gives STATUS_SUCCESS.

dlls/ntdll/nt.c

@@ -605,7 +605,7 @@ NTSTATUS WINAPI NtQuerySystemInformation(
             sbi.bKeNumberProcessors = 1; /* FIXME */
             len = sizeof(sbi);
 
-            if ( Length >= len)
+            if ( Length == len)
             {
                 if (!SystemInformation) ret = STATUS_ACCESS_VIOLATION;
                 else memcpy( SystemInformation, &sbi, len);

dlls/ntdll/tests/info.c

@@ -78,6 +78,11 @@ static void test_query_basic()
     status = pNtQuerySystemInformation(SystemBasicInformation, &sbi, sizeof(sbi), NULL);
     ok( status == STATUS_SUCCESS, "Expected STATUS_SUCCESS, got %08lx\n", status);
 
+    /* Check a too large buffer size */
+    trace("Check a too large buffer size\n");
+    status = pNtQuerySystemInformation(SystemBasicInformation, &sbi, sizeof(sbi) * 2, &ReturnLength);
+    ok( status == STATUS_INFO_LENGTH_MISMATCH, "Expected STATUS_INFO_LENGTH_MISMATCH, got %08lx\n", status);
+
     /* Finally some correct calls */
     trace("Check with correct parameters\n");
     status = pNtQuerySystemInformation(SystemBasicInformation, &sbi, sizeof(sbi), &ReturnLength);