linux-ext4 - Re: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 24 Oct 2017 15:10:07 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-ext4@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-api@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and
 MAP_SYNC

On Tue, Oct 24, 2017 at 05:24:15PM +0200, Jan Kara wrote:
> Signed-off-by: Jan Kara <jack@...e.cz>

This looks unchanged since the previous version?

> ---
>  man2/mmap.2 | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index 47c3148653be..598ff0c64f7f 100644
> --- a/man2/mmap.2
> +++ b/man2/mmap.2
> @@ -125,6 +125,21 @@ are carried through to the underlying file.
>  to the underlying file requires the use of
>  .BR msync (2).)
>  .TP
> +.B MAP_SHARED_VALIDATE
> +The same as
> +.B MAP_SHARED
> +except that
> +.B MAP_SHARED
> +mappings ignore unknown flags in
> +.IR flags .
> +In contrast when creating mapping of
> +.B MAP_SHARED_VALIDATE
> +mapping type, the kernel verifies all passed flags are known and fails the
> +mapping with
> +.BR EOPNOTSUPP
> +otherwise. This mapping type is also required to be able to use some mapping
> +flags.
> +.TP
>  .B MAP_PRIVATE
>  Create a private copy-on-write mapping.
>  Updates to the mapping are not visible to other processes
> @@ -352,6 +367,21 @@ option.
>  Because of the security implications,
>  that option is normally enabled only on embedded devices
>  (i.e., devices where one has complete control of the contents of user memory).
> +.TP
> +.BR MAP_SYNC " (since Linux 4.15)"
> +This flags is available only with
> +.B MAP_SHARED_VALIDATE
> +mapping type. Mappings of
> +.B MAP_SHARED
> +type will silently ignore this flag.
> +This flag is supported only for files supporting DAX (direct mapping of persistent
> +memory). For other files, creating mapping with this flag results in
> +.B EOPNOTSUPP
> +error. Shared file mappings with this flag provide the guarantee that while
> +some memory is writeably mapped in the address space of the process, it will
> +be visible in the same file at the same offset even after the system crashes or
> +is rebooted. This allows users of such mappings to make data modifications
> +persistent in a more efficient way using appropriate CPU instructions.
>  .PP
>  Of the above flags, only
>  .B MAP_FIXED
> -- 
> 2.12.3
>