Hi Manfred, On Fri, 2013-09-27 at 07:45 +0200, Manfred Spraul wrote: > Hi Davidlohr, > > On 09/16/2013 05:04 AM, Davidlohr Bueso wrote: > > This fixes a race in shmat() between finding the msq and > > actually attaching the segment, as another thread can delete shmid > > underneath us if we are preempted before acquiring the kern_ipc_perm.lock. > According the the man page, Linux supports attaching to deleted shm > segments: > > http://linux.die.net/man/2/shmat > > > > On Linux, it is possible to attach a shared memory segment even if it > > is already marked to be deleted. However, POSIX.1-2001 does not > > specify this behavior and many other implementations do not support it. > >
Good catch! > Does your patch change that? Yes, it should and furthermore it affects the following property: shm_nattch is decremented by one. If it becomes 0 and the segment is marked for deletion, the segment is deleted. > Unfortunately, I have neither any experience with ipc/shm nor any test > cases. > > And: > As far as I can see it's not a problem if we are attaching to a deleted > segment: shm_close cleans up everything. Agreed, please disregard this patch. Thanks, Davidlohr -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
