Re: [PATCH for-4.22 v1] tools/ocaml: xenbus - Fix handling of requests with len = 0 for socket connections

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 7/14/26 12:26 PM, Andrew Cooper wrote:
> On 09/07/2026 1:00 pm, Andrii Sultanov wrote:
> > Following the report at 
> > https://lore.kernel.org/xen-devel/CAFLBxZaeTMcF4tcV45MJdCVx4A6qbzQdjKei_Quh_iLrtARVFA@xxxxxxxxxxxxxx/
> >
> > Without this fix, the backend would be stuck waiting on the zero-sized
> > body until the next request comes in.
> >
> > Instead return the request immediately after reading the header, there's
> > no need to wait for another call to .has_more_input and .input
> >
> > Reported-by: George Dunlap <dunlapg@xxxxxxxxx>
> > Signed-off-by: Andrii Sultanov <andriy.sultanov@xxxxxxxxxx>
> Oleksii: I'm requesting a release ack on this patch.  It has been
> reviewed
> (1783604323.8631fc262581453bbf619ec5b2062170.19f471a22b0000edb5@xxxxxxxxxx
> but on a disconnected thread).
>
> There have been two bug reports so far; George (on list), and Benny (on
> Matrix).
>
> It is logically a regression vs 4.21.  A new feature in 4.22 causes `xl
> list -l`, `xl migrate`, etc to hang when using the oxenstored rather
> than (C)xenstored.
>
> There was no reply at first because the security team were investigating
> a potential security angle, but we've concluded that there isn't one.
>
> Technically a form of this bug exists in 4.21 also, but it's not used
> automatically on any path.  It's triggerable by `xl list -x` and nothing
> else we're aware of.
>
> Anyway, oxenstored is the default xenstored if you have Ocaml tools in
> the build, so this is a critical bug in 4.22.
I think this could reasonably be considered a critical bug. It affects a 
default Xen configuration (when OCaml tools are enabled and oxenstored 
is used) and causes core `xl` operations such as `xl list -l` and `xl 
migrate` to hang indefinitely. So:
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Thanks.

~ Oleksii