Index: qemu/linux-user/syscall.c
===================================================================
--- qemu.orig/linux-user/syscall.c	2007-11-28 16:36:53.000000000 -0700
+++ qemu/linux-user/syscall.c	2007-11-28 17:03:31.000000000 -0700
@@ -5399,7 +5399,7 @@
 
             grouplist = alloca(gidsetsize * sizeof(gid_t));
             ret = get_errno(getgroups(gidsetsize, grouplist));
-            if (!is_error(ret)) {
+            if (!is_error(ret) && arg1) {
                 target_grouplist = lock_user(VERIFY_WRITE, arg2, gidsetsize * 2, 0);
                 if (!target_grouplist)
                     goto efault;
@@ -5549,7 +5549,7 @@
 
             grouplist = alloca(gidsetsize * sizeof(gid_t));
             ret = get_errno(getgroups(gidsetsize, grouplist));
-            if (!is_error(ret)) {
+            if (!is_error(ret) && arg1) {
                 target_grouplist = lock_user(VERIFY_WRITE, arg2, gidsetsize * 4, 0);
                 if (!target_grouplist) {
                     ret = -TARGET_EFAULT;