[ 3.5.y.z extended stable ] Patch "xen/io/ring.h: new macro to detect whether there are too many" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 360a3e3fe9fa5a6d71933bab0f40d42083a53e9f Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich at suse.com>
Date: Mon, 17 Jun 2013 15:16:33 -0400
Subject: [PATCH] xen/io/ring.h: new macro to detect whether there are too many
 requests on the ring

commit 8d9256906a97c24e97e016482b9be06ea2532b05 upstream.

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 at oracle.com>.

Signed-off-by: Jan Beulich <jbeulich at suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 include/xen/interface/io/ring.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h
index 75271b9..7d28aff 100644
--- a/include/xen/interface/io/ring.h
+++ b/include/xen/interface/io/ring.h
@@ -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;				\
--
1.8.3.2