From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> To: "Joel Fernandes (Google)" <joel@joelfernandes.org>, linux-kernel@vger.kernel.org Cc: mtk.manpages@gmail.com, Andrew Morton <akpm@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, dancol@google.com, Jann Horn <jannh@google.com>, John Stultz <john.stultz@linaro.org>, kernel-team@android.com, linux-api@vger.kernel.org, linux-man@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox <willy@infradead.org>, Mike Kravetz <mike.kravetz@oracle.com>, Shuah Khan <shuah@kernel.org>, Stephen Rothwell <sfr@canb.auug.org.au> Subject: Re: [PATCH -manpage 1/2] fcntl.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal Date: Sat, 8 Feb 2020 12:58:07 +0100 [thread overview] Message-ID: <11efee1c-0b65-2e51-0aa6-7f61fd2958c5@gmail.com> (raw) In-Reply-To: <20190314214844.207430-2-joel@joelfernandes.org> Hello Joel, On 3/14/19 10:48 PM, Joel Fernandes (Google) wrote: > More details of the seal can be found in the LKML patch: > https://lore.kernel.org/lkml/20181120052137.74317-1-joel@joelfernandes.org/T/#t > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Thanks. Patch (finally) applied! Cheers, Michael > --- > man2/fcntl.2 | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/man2/fcntl.2 b/man2/fcntl.2 > index fce4f4c2b3bd..e01e2c075b5b 100644 > --- a/man2/fcntl.2 > +++ b/man2/fcntl.2 > @@ -1525,6 +1525,21 @@ Furthermore, if there are any asynchronous I/O operations > .RB ( io_submit (2)) > pending on the file, > all outstanding writes will be discarded. > +.TP > +.BR F_SEAL_FUTURE_WRITE > +If this seal is set, the contents of the file can be modified only from > +existing writeable mappings that were created prior to the seal being set. > +Any attempt to create a new writeable mapping on the memfd via > +.BR mmap (2) > +will fail with > +.BR EPERM. > +Also any attempts to write to the memfd via > +.BR write (2) > +will fail with > +.BR EPERM. > +This is useful in situations where existing writable mapped regions need to be > +kept intact while preventing any future writes. For example, to share a > +read-only memory buffer to other processes that only the sender can write to. > .\" > .SS File read/write hints > Write lifetime hints can be used to inform the kernel about the relative > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
WARNING: multiple messages have this Message-ID (diff)
From: "Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> To: "Joel Fernandes (Google)" <joel-QYYGw3jwrUn5owFQY34kdNi2O/JbrIOy@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, dancol-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, Jann Horn <jannh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, John Stultz <john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, kernel-team-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Mike Kravetz <mike.kravetz-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, Shuah Khan <shuah-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Stephen Rothwell <sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org> Subject: Re: [PATCH -manpage 1/2] fcntl.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal Date: Sat, 8 Feb 2020 12:58:07 +0100 [thread overview] Message-ID: <11efee1c-0b65-2e51-0aa6-7f61fd2958c5@gmail.com> (raw) In-Reply-To: <20190314214844.207430-2-joel-QYYGw3jwrUn5owFQY34kdNi2O/JbrIOy@public.gmane.org> Hello Joel, On 3/14/19 10:48 PM, Joel Fernandes (Google) wrote: > More details of the seal can be found in the LKML patch: > https://lore.kernel.org/lkml/20181120052137.74317-1-joel-QYYGw3jwrUn5owFQY34kdNi2O/JbrIOy@public.gmane.org/T/#t > > Signed-off-by: Joel Fernandes (Google) <joel-QYYGw3jwrUn5owFQY34kdNi2O/JbrIOy@public.gmane.org> Thanks. Patch (finally) applied! Cheers, Michael > --- > man2/fcntl.2 | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/man2/fcntl.2 b/man2/fcntl.2 > index fce4f4c2b3bd..e01e2c075b5b 100644 > --- a/man2/fcntl.2 > +++ b/man2/fcntl.2 > @@ -1525,6 +1525,21 @@ Furthermore, if there are any asynchronous I/O operations > .RB ( io_submit (2)) > pending on the file, > all outstanding writes will be discarded. > +.TP > +.BR F_SEAL_FUTURE_WRITE > +If this seal is set, the contents of the file can be modified only from > +existing writeable mappings that were created prior to the seal being set. > +Any attempt to create a new writeable mapping on the memfd via > +.BR mmap (2) > +will fail with > +.BR EPERM. > +Also any attempts to write to the memfd via > +.BR write (2) > +will fail with > +.BR EPERM. > +This is useful in situations where existing writable mapped regions need to be > +kept intact while preventing any future writes. For example, to share a > +read-only memory buffer to other processes that only the sender can write to. > .\" > .SS File read/write hints > Write lifetime hints can be used to inform the kernel about the relative > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
next prev parent reply other threads:[~2020-02-08 11:58 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-03-14 21:48 [PATCH -manpage 0/2] Joel Fernandes (Google) 2019-03-14 21:48 ` [PATCH -manpage 1/2] fcntl.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal Joel Fernandes (Google) 2020-02-08 11:58 ` Michael Kerrisk (man-pages) [this message] 2020-02-08 11:58 ` Michael Kerrisk (man-pages) 2019-03-14 21:48 ` [PATCH -manpage 2/2] memfd_create.2: " Joel Fernandes (Google) 2020-02-08 11:58 ` Michael Kerrisk (man-pages) 2020-02-08 11:58 ` Michael Kerrisk (man-pages) -- strict thread matches above, loose matches on Subject: below -- 2019-01-13 0:14 [PATCH -manpage 0/2] Document " Joel Fernandes 2019-01-13 0:14 ` [PATCH -manpage 1/2] fcntl.2: Update manpage with new " Joel Fernandes 2018-12-12 22:05 Joel Fernandes (Google) 2018-11-20 5:25 Joel Fernandes (Google) 2018-11-20 5:25 ` Joel Fernandes (Google) 2018-11-20 5:25 ` joel
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