linux-kernel - Re: [PATCH v6 0/8] ipc: Clamp *mni to the real IPCMNI limit & increase that limit

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Message-ID: <a767b365-0646-55fe-6c23-f05c212c9104@redhat.com>
Date:   Mon, 7 May 2018 15:14:28 -0400
From:   Waiman Long <longman@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v6 0/8] ipc: Clamp *mni to the real IPCMNI limit &
 increase that limit

On 05/02/2018 11:06 AM, Eric W. Biederman wrote:
>
>>> and or users that may or may not exist.  If you can find something that
>>> will care sure.  We need to avoid breaking userspace and causing
>>> regressions.  However as this stands it looks you are making maintenance
>>> of the kernel more difficult to avoid having to look to see if there are
>>> monsters under the bed.
>> I shall admit that it can be hard to find applications that will
>> explicitly need that as we usually don't have access to the applications
>> that the customers have. It is more a correctness issue where the
>> existing code is kind of lying about what can actually be supported. I
>> just want to make the users more aware of what the right limits are.
> You presume the kernel is lying to applications.  I admit the kernel
> can lie to applications.  I don't see any evidence that the kernel is
> actually doing so.  So far (to me) it looks like a large number of sysv
> shared memory segments is not particulalry common.
>
> So I would not be at all surprised if no regressions would be generated
> if you simply deny setting the value past the maximum.

Maybe you are right. I will update the patchset to fail the update if
the range is exceeded since I had added option of extending the limit if
the users choose to do so.

Cheers,
Longman