Re: [PATCH] tools: xentoolcore_restrict_all: Do deregistration before close

[Julien Grall <julien.grall@linaro.org>]

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@eu.citrix.com>
> 
> Acked-by: Wei Liu <wei.liu2@citrix.com>

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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