[PATCH v3] getrandom system call wrapper [BZ #17252]

[Florian Weimer]

On 09/12/2016 09:25 AM, Florian Weimer wrote:
> On 09/09/2016 05:23 PM, Torvald Riegel wrote:
>> On Fri, 2016-09-09 at 16:28 +0200, Florian Weimer wrote:
>>> On 09/09/2016 04:21 PM, Torvald Riegel wrote:
>>>> On Thu, 2016-09-08 at 13:44 +0200, Florian Weimer wrote:
>>>>> I have made the system call wrapper a cancellation point.  (If we
>>>>> implement the simpler getentropy interface, it would not be a
>>>>> cancellation point.)
>>>>
>>>> Why did you do that?
>>>
>>> I have to, because it can block indefinitely.
>>
>> That doesn't mean you have to make the default function a cancellation
>> point.  There are many POSIX functions which can block indefinitely and
>> which are not required to be cancellation points (eg, rwlocks only *may*
>> be cancellation points).
>>
>> Can the system call really block indefinitely, or only for a long time
>> and (ie, will return eventually)?
>
> Yes, if the system enters a deadlock condition where the waiting for
> randomness prevents it from accumulating additional randomness.

This is what happens here:

   <https://bugzilla.redhat.com/show_bug.cgi?id=1383060>

systemd will eventually kill the blocked process and the boot continues, 
but all network services will be missing.

Florian