Re: GPF in shm_lock ipc

From	Manfred Spraul <manfred@colorfullife.com>
Newsgroups	linux.kernel
Subject	Re: GPF in shm_lock ipc
Date	2016-01-02 12:40 +0100
Message-ID	<qMsHn-7xw-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <qiYi5-2kQ-5@gated-at.bofh.it> <qj721-6Fq-11@gated-at.bofh.it> <qoXt0-20k-3@gated-at.bofh.it> <qrtI6-7PQ-11@gated-at.bofh.it> <qIaSK-8ka-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Dmitry,

shm locking differs too much from msg/sem locking, I never looked at it 
in depth, so I'm not able to perform a proper review.

Except for the obvious: Races that can be triggered from user space are 
inacceptable.
Regardless if there is a BUG_ON, a WARN_ON or nothing at all.

On 12/21/2015 04:44 PM, Dmitry Vyukov wrote:
>> +
>> +/* This is called by fork, once for every shm attach. */
>> +static void shm_open(struct vm_area_struct *vma)
>> +{
>> +       int err = __shm_open(vma);
>> +       /*
>> +        * We raced in the idr lookup or with shm_destroy().
>> +        * Either way, the ID is busted.
>> +        */
>> +       WARN_ON_ONCE(err);
>>   }
Is it possible to trigger this race? Parallel IPC_RMID & fork()?

--
     Manfred
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Thread

Re: GPF in shm_lock ipc Dmitry Vyukov <dvyukov@google.com> - 2015-12-21 16:50 +0100
  Re: GPF in shm_lock ipc Manfred Spraul <manfred@colorfullife.com> - 2016-01-02 12:40 +0100
    Re: GPF in shm_lock ipc Dmitry Vyukov <dvyukov@google.com> - 2016-01-02 13:30 +0100
      Re: GPF in shm_lock ipc Manfred Spraul <manfred@colorfullife.com> - 2016-01-02 17:00 +0100

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