Re: [PATCH 2/4] ipc,shm: prevent race with rmid in shmat(2)

[Manfred Spraul]

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/