snapd and semaphores

[Jamie Strandboge]

On Mon, 2017-01-02 at 16:34 +0100, Olivier Tilloy wrote:
> Hi everyone, and happy new year!
> 
> I’m snapping an app that makes use of semaphores¹ and seeing an
> apparmor denial. The glibc implementation of sem_open calls
> SHM_GET_NAME(EINVAL,SEM_FAILED,SEM_SHM_PREFIX) where SEM_SHM_PREFIX is
> "sem.", so it tries to create /dev/shm/sem.{name}, which fails because
> snapd only allows /dev/shm/snap.@{SNAP_NAME}.**.
> At a quick glance, there’s no mechanism (e.g. env var) to customize
> the prefix ("sem.").
> Is this an issue others have run into? Is there a recommended solution?
> 
> Thanks in advance!
> 

Reading sem_overview, it seems that we should also allow:
'/dev/shm/sem.snap.@{SNAP_NAME}.*'. In this manner, we namespace /dev/shm/sem.*
by snap name just like we do other parts of the OS. Please file a bug and we'll
get this fixed.

Thanks!

-- 
Jamie Strandboge             | http://www.canonical.com

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