Re: [Xen-devel] [PATCH] tools: xentoolcore_restrict_all: Do deregistration before close

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi,

On 14/11/17 14:02, Wei Liu wrote:
> On Tue, Nov 14, 2017 at 12:15:42PM +0000, Ian Jackson wrote:
> > Closing the fd before unhooking it from the list runs the risk that a
> > concurrent thread calls xentoolcore_restrict_all will operate on the
> > old fd value, which might refer to a new fd by then.  So we need to do
> > it in the other order.
> >
> > Sadly this weakens the guarantee provided by xentoolcore_restrict_all
> > slight, but not (I think) in a problematic way.  It would be possible
> slightly
>
> > to implement the previous guarantee, but it would involve replacing
> > all of the close() calls in all of the individual osdep parts of all
> > of the individual libraries with calls to a new function which does
> >     dup2("/dev/null", thing->fd);
> >     pthread_mutex_lock(&handles_lock);
> >     thing->fd = -1;
> >     pthread_mutex_unlock(&handles_lock);
> >     close(fd);
> > which would be terribly tedious.
> >
> > Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
I think this is 4.10 material, xentoolcore was introduced in this 
release and it would be good to have it right from now. I want to 
confirm that you are both happy with that?
Cheers,

--
Julien Grall

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