From: Dan Williams <dan.j.williams@intel.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Christoph Hellwig <hch@infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Linux MM <linux-mm@kvack.org>,
Linux API <linux-api@vger.kernel.org>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Kees Cook <keescook@chromium.org>,
Florian Weimer <fweimer@redhat.com>,
John Hubbard <jhubbard@nvidia.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 01/18] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags
Date: Wed, 22 Nov 2017 08:52:37 -0800 [thread overview]
Message-ID: <CAPcyv4gGRHWc6AH5Enb7njtmqHgd=g+0-mYMdd5wWjJMW0+d7g@mail.gmail.com> (raw)
In-Reply-To: <638b3b80-5cb9-97c2-5055-fef3a1ec25b9@suse.cz>
On Wed, Nov 22, 2017 at 4:02 AM, Vlastimil Babka <vbabka@suse.cz> wrote:
> On 11/01/2017 04:36 PM, Jan Kara wrote:
>> From: Dan Williams <dan.j.williams@intel.com>
>>
>> The mmap(2) syscall suffers from the ABI anti-pattern of not validating
>> unknown flags. However, proposals like MAP_SYNC 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.
>
> So I'm trying to make sense of this together with Michal's attempt for
> MAP_FIXED_SAFE [1] where he has to introduce a completely new flag
> instead of flag modifier exactly for the reason of not validating
> unknown flags. And my conclusion is that because MAP_SHARED_VALIDATE
> implies MAP_SHARED and excludes MAP_PRIVATE, MAP_FIXED_SAFE as a
> modifier cannot build on top of this. Wouldn't thus it be really better
> long-term to introduce mmap3 at this point? ...
We have room to define MAP_PRIVATE_VALIDATE in MAP_TYPE on every arch
except parisc. Can we steal an extra bit for MAP_TYPE from somewhere
else on parisc?
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next prev parent reply other threads:[~2017-11-22 16:52 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-01 15:36 [PATCH 0/18 v6] dax, ext4, xfs: Synchronous page faults Jan Kara
2017-11-01 15:36 ` [PATCH 01/18] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Jan Kara
2017-11-22 12:02 ` Vlastimil Babka
2017-11-22 16:52 ` Dan Williams [this message]
2017-11-22 19:53 ` Matthew Wilcox
2017-11-25 18:45 ` Helge Deller
2017-11-27 15:55 ` Vlastimil Babka
2017-11-01 15:36 ` [PATCH 02/18] mm: Remove VM_FAULT_HWPOISON_LARGE_MASK Jan Kara
2017-11-01 15:36 ` [PATCH 03/18] dax: Simplify arguments of dax_insert_mapping() Jan Kara
2017-11-01 15:36 ` [PATCH 04/18] dax: Factor out getting of pfn out of iomap Jan Kara
2017-11-01 15:36 ` [PATCH 05/18] dax: Create local variable for VMA in dax_iomap_pte_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 06/18] dax: Create local variable for vmf->flags & FAULT_FLAG_WRITE test Jan Kara
2017-11-01 15:36 ` [PATCH 07/18] dax: Inline dax_insert_mapping() into the callsite Jan Kara
2017-11-01 15:36 ` [PATCH 08/18] dax: Inline dax_pmd_insert_mapping() " Jan Kara
2017-11-01 15:36 ` [PATCH 09/18] dax: Fix comment describing dax_iomap_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 10/18] dax: Allow dax_iomap_fault() to return pfn Jan Kara
2017-11-01 15:36 ` [PATCH 11/18] dax: Allow tuning whether dax_insert_mapping_entry() dirties entry Jan Kara
2017-11-01 15:36 ` [PATCH 12/18] mm: Define MAP_SYNC and VM_SYNC flags Jan Kara
2017-11-01 15:36 ` [PATCH 13/18] dax, iomap: Add support for synchronous faults Jan Kara
2017-11-01 15:36 ` [PATCH 14/18] dax: Implement dax_finish_sync_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 15/18] ext4: Simplify error handling in ext4_dax_huge_fault() Jan Kara
2017-11-01 15:36 ` [PATCH 16/18] ext4: Support for synchronous DAX faults Jan Kara
2017-11-01 15:36 ` [PATCH 17/18] xfs: Implement xfs_filemap_pfn_mkwrite() using __xfs_filemap_fault() Jan Kara
2017-11-14 2:19 ` Darrick J. Wong
2017-11-01 15:36 ` [PATCH 18/18] xfs: support for synchronous DAX faults Jan Kara
2017-11-14 2:19 ` Darrick J. Wong
2017-11-01 15:36 ` [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Jan Kara
2018-04-12 13:00 ` Michael Kerrisk (man-pages)
2018-04-12 14:00 ` Ross Zwisler
2018-04-12 14:22 ` Jan Kara
2018-04-12 18:20 ` Michael Kerrisk (man-pages)
2018-04-13 11:17 ` Jan Kara
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