Commit 8d925690 authored Jun 17, 2013 by Jan Beulich Committed by Konrad Rzeszutek Wilk Jun 17, 2013

xen/io/ring.h: new macro to detect whether there are too many requests on the ring



Backends may need to protect themselves against an insane number of
produced requests stored by a frontend, in case they iterate over
requests until reaching the req_prod value. There can't be more
requests on the ring than the difference between produced requests
and produced (but possibly not yet published) responses.

This is a more strict alternative to a patch previously posted by
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

parent 604c499c

include/xen/interface/io/ring.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -188,6 +188,11 @@ struct __name##_back_ring { \
		#define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
		(((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))

		/* Ill-behaved frontend determination: Can there be this many requests? */
		#define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
		(((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))


		#define RING_PUSH_REQUESTS(_r) do { \
		wmb(); /* back sees requests /before/ updated producer index */ \
		(_r)->sring->req_prod = (_r)->req_prod_pvt; \