[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@xxxxxxxxxx>
http://karelzak.blogspot.com
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