On Thu, Apr 19, 2012 at 11:07:55AM +0200, Lukas Czerner wrote:
> Some mount flags can conflict with each other so they can not be
> handled together. Currently when conflicting flags are specified,
> some of them are silently ignored putting user in believe that
> they was handled correctly.
Unfortunately, it's not so simple ;-)
> - if (flags & MS_REMOUNT)
> + if (flags & MS_REMOUNT) {
> retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
> data_page);
> - else if (flags & MS_BIND)
> + flags &= ~MS_REMOUNT;
This is incorrect, the flags may also include many others flags. For
example MS_REMOUNT|MS_BIND|MS_RDONLY is valid (see do_remoun() code).
And it's normal that for "mount -o remount" the mount command reads
flags from mtab/fstab so it includes for example MS_RELATIME, ...
> + } else if (flags & MS_BIND) {
> retval = do_loopback(&path, dev_name, flags & MS_REC);
> - else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
> + flags &= ~MS_BIND;
what about MS_REC ?
> + } else if (flags & (MS_SHARED | MS_PRIVATE |
> + MS_SLAVE | MS_UNBINDABLE)) {
> retval = do_change_type(&path, flags);
> - else if (flags & MS_MOVE)
> + flags &= ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE);
what about MS_REC ?
Note that do_change_type() already checks for unexpected flags and
returns -EINVAL if more flags are specified.
> + } else if (flags & MS_MOVE) {
> retval = do_move_mount(&path, dev_name);
> - else
> + flags &= ~MS_MOVE;
> + } else
> retval = do_new_mount(&path, type_page, flags, mnt_flags,
> dev_name, data_page);
> +
> + flags &= (MS_REMOUNT | MS_BIND | MS_SHARED | MS_PRIVATE |
> + MS_SLAVE | MS_UNBINDABLE | MS_MOVE);
> +
> + if (!retval && flags)
> + printk(KERN_WARNING "%s(%u): (%s -> %s) Conflicting mount flags"
> + " specified. These flags has been "
> + "ignored: %#.8lx\n", __func__, current->pid,
> + dev_name, dir_name, flags);
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
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