From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 06 May 2004 09:30:23 +0000
Subject: Re: [PATCH] udev callout for reading filesystem labels
Message-Id: <200405061130.26733.arnd@arndb.de>
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On Thursday 29 April 2004 23:04, Kay Sievers wrote:
> Hi,
> here is a small udev toy, which enables udev to name partitions by
> its filesystem label or uuid's.
>=20
> The following udev rule:
>=20
> =A0 KERNEL=3D"sd*", PROGRAM=3D"/sbin/udev_volume_id -M%M -m%m -u", SYMLIN=
K=3D"%c"
>=20
> creates a symlink with the uuid read from the filesystem. If no label or
> uuid is found the program exits with nonzero and the rule will fail.

Cool. I've tried to do something similar for dasd device labels before
but not come up with a working solution yet.

Do you think that udev_volume_id can be extended so that it can also
read disk labels and not just partition labels? The method for
detecting and reading a dasd label is the same as for fs labels,
and I have the necessary parsing code here.

The trouble is that the label is stored in the partition table, not
in the partition itself, so I would need to pass the minor number
from e.g. block/dasda/dev instead of block/dasda/dasda{1,2,3}/dev
to udev_volume_id.

> +/* open volume by major/minor */
> +struct volume_id *volume_id_open_dev_t(dev_t devt)
> +{
> +=A0=A0=A0=A0=A0=A0=A0struct volume_id *id;
> +=A0=A0=A0=A0=A0=A0=A0char tmp_node[VOLUME_ID_PATH_MAX];
> +
> +=A0=A0=A0=A0=A0=A0=A0snprintf(tmp_node, VOLUME_ID_PATH_MAX,
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 "/tmp/volume-%u-%u", major=
(devt), minor(devt));
> +=A0=A0=A0=A0=A0=A0=A0tmp_node[VOLUME_ID_PATH_MAX] =3D '\0';

This looks like a malicious user can easily prevent it from working
by creating files in /tmp. You might need to use something similar
to tmpfile(3) here.

	Arnd <><

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