| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.4 74/99] xen/io/ring.h: new macro to detect whether there are too many requests on the ring | Date | Fri, 7 Mar 2014 17:08:10 -0800 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: Jan Beulich <jbeulich@suse.com>
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@oracle.com>.
Signed-off-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Cc: Yijing Wang <wangyijing@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- include/xen/interface/io/ring.h | 5 +++++ 1 file changed, 5 insertions(+)
--- 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; \
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