linux-kernel - Re: [RFC PATCH v8 0/5] IPC: checkpoint/restore in userspace enhancements

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Message-ID: <50D4DB5D.9020309@oracle.com>
Date:	Fri, 21 Dec 2012 16:57:49 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Stanislav Kinsbursky <skinsbursky@...allels.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	serge.hallyn@...onical.com, ebiederm@...ssion.com,
	linux-kernel@...r.kernel.org, xemul@...allels.com,
	catalin.marinas@....com, will.deacon@....com, jmorris@...ei.org,
	cmetcalf@...era.com, joe.korty@...r.com, dhowells@...hat.com,
	dledford@...hat.com, viro@...iv.linux.org.uk,
	kosaki.motohiro@...fujitsu.com, linux-api@...r.kernel.org,
	serue@...ibm.com, tglx@...utronix.de, paulmck@...ux.vnet.ibm.com,
	devel@...nvz.org, mtk.manpages@...il.com,
	Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [RFC PATCH v8 0/5] IPC: checkpoint/restore in userspace enhancements

On 12/21/2012 03:46 PM, Stanislav Kinsbursky wrote:
> 21.12.2012 00:47, Andrew Morton пишет:
>> On Thu, 20 Dec 2012 08:06:32 +0400
>> Stanislav Kinsbursky<skinsbursky@...allels.com>  wrote:
>>
>>> 19.12.2012 00:36, Andrew Morton __________:
>>>> On Wed, 24 Oct 2012 19:34:51 +0400
>>>> Stanislav Kinsbursky<skinsbursky@...allels.com>  wrote:
>>>>
>>>>> This respin of the patch set was significantly reworked. Most part of new API
>>>>> was replaced by sysctls (by one per messages, semaphores and shared memory),
>>>>> allowing to preset desired id for next new IPC object.
>>>>>
>>>>> This patch set is aimed to provide additional functionality for all IPC
>>>>> objects, which is required for migration of these objects by user-space
>>>>> checkpoint/restore utils (CRIU).
>>>>>
>>>>> The main problem here was impossibility to set up object id. This patch set
>>>>> solves the problem by adding new sysctls for preset of desired id for new IPC
>>>>> object.
>>>>>
>>>>> Another problem was to peek messages from queues without deleting them.
>>>>> This was achived by introducing of new MSG_COPY flag for sys_msgrcv(). If
>>>>> MSG_COPY flag is set, then msgtyp is interpreted as message number.
>>>> According to my extensive records, Sasha hit a bug in
>>>> ipc-message-queue-copy-feature-introduced.patch and Fengguang found a
>>>> bug in
>>>> ipc-message-queue-copy-feature-introduced-cleanup-do_msgrcv-aroung-msg_copy-feature.patch
>>>>
>>>> It's not obvious (to me) that these things have been identified and
>>>> fixed.  What's the status, please?
>>> Hello, Andrew.
>>> Fengguang's issue was solved by "ipc: simplify message copying" I sent you.
>>> But I can't find Sasha's issue. As I remember, there was some problem in
>>> early
>>> version of the patch set. But I believe its fixed now.
>> http://lkml.indiana.edu/hypermail/linux/kernel/1210.3/01710.html
>>
>> Subject: "ipc, msgqueue: NULL ptr deref in msgrcv"
> 
> Ah, yes. Thanks.
> Hi found it in initial version of code, which was significantly changed (or cleaned and simplified) by further patch series.
> And I cant find out, how this can happen, because this patch he bisect to do not modify the queue itself, while he found the
> problem in testmsg.

I actually can't reproduce it on the latest -next.

I was reverting the IPC changes in the past couple of weeks so that I could test the
rest of the IPC code with the fuzzer, and when I added them back in again I can't
reproduce the issue I've reported earlier.

We can probably figure out where it got fixed by bisecting between -next trees if anyone
is interested in that.


Thanks,
Sasha

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