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SubjectRe: [PATCH 2/4] ipc,shm: prevent race with rmid in shmat(2)
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.
>
Does your patch change that?
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.

--
Manfred


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