Restoring permissions on existing nodes

Restoring permissions on existing nodes

[Martin Orr]

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Is there a reason why udev sets the permissions and SELinux context every
time it finds an existing node or symlink?

The code in question is (from udev_node.c):

in udev_node_mknod():
if ((stats.st_mode & S_IFMT) == (mode & S_IFMT) && (stats.st_rdev == devt)) {
	info("preserve file '%s', because it has correct dev_t", file);
	selinux_setfilecon(file, udev->dev->kernel, stats.st_mode);
	goto perms;
}

in node_symlink():
if (strcmp(target, buf) == 0) {
	info("preserve already existing symlink '%s' to '%s'", slink, target);
	selinux_setfilecon(slink, NULL, S_IFLNK);
	goto exit;
}

-- 
Martin Orr


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Re: Restoring permissions on existing nodes

[Kay Sievers]

On Dec 3, 2007 1:13 PM, Martin Orr <martin@martinorr.name> wrote:
> Is there a reason why udev sets the permissions and SELinux context every
> time it finds an existing node or symlink?
>
> The code in question is (from udev_node.c):
>
> in udev_node_mknod():
> if ((stats.st_mode & S_IFMT) = (mode & S_IFMT) && (stats.st_rdev = devt)) {
>         info("preserve file '%s', because it has correct dev_t", file);
>         selinux_setfilecon(file, udev->dev->kernel, stats.st_mode);
>         goto perms;
> }
>
> in node_symlink():
> if (strcmp(target, buf) = 0) {
>         info("preserve already existing symlink '%s' to '%s'", slink, target);
>         selinux_setfilecon(slink, NULL, S_IFLNK);
>         goto exit;
> }

Because it should match what the configuration specifies, you
can't expect that the properties of a pre-existing node are correct.
The node does not get replaced, because it should not change the inode
number, but all other properties get re-applied with the configured
values or the built-in default.

Kay

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