Re: [Qemu-devel] [Xen-devel] [PATCH] xenfb.c: avoid expensive loops when prod <= out_cons

[David Vrabel]

On 06/01/16 12:08, Stefano Stabellini wrote:
> If the frontend sets out_cons to a value higher than out_prod, it will
> cause xenfb_handle_events to loop about 2^32 times. Avoid that by using
> better checks at the beginning of the function.

You can't use less than to compare prod and cons because they wrap.

You need to compare (prod - cons) against ring size (or similar) to
check for overflow.  See RING_REQUEST_PROD_OVERFLOW() etc.

David