linux-kernel - Re: [PATCH v4 0/4] Application Data Integrity feature introduced by SPARC M7

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Message-ID: <815b1871-5353-deb9-2091-0803bec029b7@oracle.com>
Date:   Fri, 13 Jan 2017 10:36:26 -0700
From:   Rob Gardner <rob.gardner@...cle.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Khalid Aziz <khalid.aziz@...cle.com>, davem@...emloft.net,
        corbet@....net, arnd@...db.de, akpm@...ux-foundation.org
Cc:     hpa@...or.com, viro@...iv.linux.org.uk, nitin.m.gupta@...cle.com,
        chris.hyser@...cle.com, tushar.n.dave@...cle.com,
        sowmini.varadhan@...cle.com, mike.kravetz@...cle.com,
        adam.buchbinder@...il.com, minchan@...nel.org, hughd@...gle.com,
        kirill.shutemov@...ux.intel.com, keescook@...omium.org,
        allen.pais@...cle.com, aryabinin@...tuozzo.com,
        atish.patra@...cle.com, joe@...ches.com, pmladek@...e.com,
        jslaby@...e.cz, cmetcalf@...lanox.com,
        paul.gortmaker@...driver.com, mhocko@...e.com, jmarchan@...hat.com,
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        tglx@...utronix.de, mingo@...hat.com, dan.j.williams@...el.com,
        iamjoonsoo.kim@....com, mgorman@...hsingularity.net,
        vdavydov.dev@...il.com, hannes@...xchg.org, namit@...are.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-arch@...r.kernel.org,
        x86@...nel.org, linux-mm@...ck.org
Subject: Re: [PATCH v4 0/4] Application Data Integrity feature introduced by
 SPARC M7

On 01/13/2017 09:08 AM, Dave Hansen wrote:
> On 01/13/2017 07:29 AM, Rob Gardner wrote:
>> so perhaps ADI should simply be disallowed for memory mapped to
>> files, and this particular complication can be avoided. Thoughts?
> What's a "file" from your perspective?
>
> In Linux, shared memory is a file.  hugetlbfs is done with files.  Many
> databases mmap() their data into their address space.

Of course I meant a traditional file is the DOS sense, ie, data stored 
on something magnetic. ;) But it doesn't really matter because I am just 
trying to envision a use case for any of the mmap scenarios.

For instance a very persuasive use case for ADI is to 'color' malloc 
memory, freed malloc memory, and malloc's metadata with different ADI 
version tags so as to catch buffer overflows, underflows, use-after-free 
and use-after-realloc type scenarios. What is an equally compelling or 
even mildly interesting use case for ADI in shared memory and file mmap 
situations? Maybe you could mmap a file and immediately tag the entire 
thing with some version, thus disallowing all access to it, and then 
hand out access a chunk at a time. And then?

Rob