From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Linux API <linux-api@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, Andy Lutomirski <luto@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH v8 2/2] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags
Date: Mon, 11 Sep 2017 10:01:49 -0700 [thread overview]
Message-ID: <CAPcyv4iSzq=1XQEvabSmSCQ6LPU6U4QRDTSB46=SUuZGg9RAfA@mail.gmail.com> (raw)
In-Reply-To: <20170911111030.GA20127@lst.de>
On Mon, Sep 11, 2017 at 4:10 AM, Christoph Hellwig <hch@lst.de> wrote:
> On Mon, Sep 11, 2017 at 11:47:14AM +0200, Jan Kara wrote:
>> On Fri 08-09-17 12:35:13, Dan Williams wrote:
>> > The mmap(2) syscall suffers from the ABI anti-pattern of not validating
>> > unknown flags. However, proposals like MAP_SYNC and MAP_DIRECT need a
>> > mechanism to define new behavior that is known to fail on older kernels
>> > without the support. Define a new MAP_SHARED_VALIDATE flag pattern that
>> > is guaranteed to fail on all legacy mmap implementations.
>> >
>> > With this in place new flags can be defined as:
>> >
>> > #define MAP_new (MAP_SHARED_VALIDATE | val)
>>
>> Is this changelog stale? Given MAP_SHARED_VALIDATE will be new mapping
>> type, I'd expect we define new flags just as any other mapping flags...
>> I see no reason why MAP_SHARED_VALIDATE should be or'ed to that.
>
> Btw, I still think it should be a new hidden flag and not a new mapping
> type. I brought this up last time, so maybe I missed the answer
> to my concern.
>
I thought you agreed to MAP_SHARED_VALIDATE here:
https://marc.info/?l=linux-mm&m=150425124907931&w=2
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next prev parent reply other threads:[~2017-09-11 17:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-08 19:35 [RFC PATCH v8 0/2] mmap: safely enable support for new flags Dan Williams
2017-09-08 19:35 ` [RFC PATCH v8 1/2] vfs: add flags parameter to all ->mmap() handlers Dan Williams
2017-09-11 9:50 ` Jan Kara
2017-09-08 19:35 ` [RFC PATCH v8 2/2] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Dan Williams
2017-09-11 9:47 ` Jan Kara
2017-09-11 11:10 ` Christoph Hellwig
2017-09-11 11:45 ` Jan Kara
2017-09-11 17:01 ` Dan Williams [this message]
2017-09-11 17:21 ` Dan Williams
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