Bug 188721

Function get_zeroed_page() returns a NULL pointer if there is no enough memory. The function xenstored_local_init() defined in file drivers/xen/xenbus/xenbus_probe.c should return a non-zero value if there is an error. However, when the call to get_zeroed_page() (at line 710) returns a NULL pointer, the return variable err still takes value 0, which may mislead the caller of xenstored_local_init(). Maybe it is better to assign "-ENOMEM" to err when get_zeroed_page() returns a NULL pointer. Codes related to this bug are summarised as follows.

xenstored_local_init @@ drivers/xen/xenbus/xenbus_probe.c
703 static int __init xenstored_local_init(void)
704 {
705     int err = 0;
706     unsigned long page = 0;
707     struct evtchn_alloc_unbound alloc_unbound;
708 
709     /* Allocate Xenstore page */
710     page = get_zeroed_page(GFP_KERNEL);
711     if (!page)
712         goto out_err;    // insert "err = -ENOMEM;" before this jump instruction?
713 
714     xen_store_gfn = xen_start_info->store_mfn = virt_to_gfn((void *)page);
715 
716     /* Next allocate a local port which xenstored can bind to */
717     alloc_unbound.dom        = DOMID_SELF;
718     alloc_unbound.remote_dom = DOMID_SELF;
719 
720     err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
721                       &alloc_unbound);
722     if (err == -ENOSYS)
723         goto out_err;
724 
725     BUG_ON(err);
726     xen_store_evtchn = xen_start_info->store_evtchn =
727         alloc_unbound.port;
728 
729     return 0;
730 
731  out_err:
732     if (page != 0)
733         free_page(page);
734     return err;
735 }

Thanks very much!