From: Karel Zak <kzak@redhat.com>
To: Phillip Susi <psusi@ubuntu.com>
Cc: util-linux@vger.kernel.org, Miklos Szeredi <miklos@szeredi.hu>
Subject: Re: read only bind mount ignores ready only
Date: Thu, 12 Dec 2013 13:05:44 +0100 [thread overview]
Message-ID: <20131212120544.GJ16572@x2.net.home> (raw)
In-Reply-To: <52A878C5.6050505@ubuntu.com>
[CC: kernel guys]
On Wed, Dec 11, 2013 at 09:37:57AM -0500, Phillip Susi wrote:
> It seems that the kernel has a bug where it silently ignores the
> MS_RDONLY flag when creating a bind mount. mount issues a warning
> that the mount point appears to be read-write even though you
> requested read only. The reporter suggests a patch to automatically
> attempt to remount with MS_RDONLY before issuing this warning to work
> around the kernel bug. What do you think?
I have it implemented, so
mount --bind --read-only /mnt /mnt
is interpreted as two requests (two mount(2) calls)
mount --bind /mnt /mnt
mount -o remount,bind,ro /tmp
it works as expected, but it does not work with MS_REC (recursive)
because kernel currently does not support
MS_REMOUNT|MS_BIND|MS_REC|...
it means that
mount --rbind --read-only /mnt /mnt
creates only top-level read-only mountpoint, the rest is unchanged.
Miklos would be possible to fix kernel to accept MS_REC for
MS_REMOUNT|MS_BIND|MS_RDONLY operation? Please.
It seems that all we need is to call stuff in mnt_make_readonly() for
all next_mnt() items.
(Well, it would be also nice to learn kernel to support
MS_BIND|MS_RDONLY, but it's probably more invasive change.)
Lare;
--
Karel Zak <kzak@redhat.com>
http://karelzak.blogspot.com
next prev parent reply other threads:[~2013-12-12 12:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-11 14:37 read only bind mount ignores ready only Phillip Susi
2013-12-11 16:49 ` Karel Zak
2013-12-12 12:05 ` Karel Zak [this message]
2013-12-12 14:59 ` Phillip Susi
2013-12-12 16:02 ` Karel Zak
2013-12-12 19:42 ` Miklos Szeredi
2013-12-12 21:53 ` Al Viro
2013-12-13 10:45 ` Karel Zak
2013-12-13 8:18 ` Karel Zak
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