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selinux: Fwd: Re: [libvirt] [PATCH] selinux: Don't fail RestoreA

Fwd: Re: [libvirt] [PATCH] selinux: Don't fail RestoreAll if file doesn't have a default label

From: Daniel J Walsh <dwalsh_at_nospam>
Date: Tue Oct 23 2012 - 10:57:25 GMT
To: SELinux <selinux@tycho.nsa.gov>

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libvirt is trying to restore the context of a path back to the default when a
virtual machine completes. One problem with this is what happens when a
virtual machine is stored in a directory like /mnt. There is no default to
set the label back to.

I have suggested either they record the old label and restore it back when the
job finishes or the walk the directory tree to set the label to the first
parent directory that has a specified label.

- -------- Original Message --------
Subject: Re: [libvirt] [PATCH] selinux: Don't fail RestoreAll if file doesn't
have a default label
Date: Mon, 22 Oct 2012 16:13:22 -0400
From: Cole Robinson <crobinso@redhat.com>
To: Eric Blake <eblake@redhat.com>
CC: libvirt-list@redhat.com, Daniel J Walsh <dwalsh@redhat.com>

On 10/22/2012 11:51 AM, Eric Blake wrote:
> On 10/21/2012 02:44 PM, Cole Robinson wrote:
>> When restoring selinux labels after a VM is stopped, any non-standard
>> path that doesn't have a default selinux label causes the process to stop
>> and exit early. This isn't really an error condition IMO.
>>
>> Of course the selinux API could be erroring for some other reason but
>> hopefully that's rare enough to not need explicit handling.
>>
>> Common example here is storing disk images in a non-standard location
>> like under /mnt. --- src/security/security_selinux.c | 4 ++++ 1 file
>> changed, 4 insertions(+)
>>
>> diff --git a/src/security/security_selinux.c
>> b/src/security/security_selinux.c index eee8d71..7681f1b 100644 ---
>> a/src/security/security_selinux.c +++ b/src/security/security_selinux.c
>> @@ -936,7 +936,11 @@ virSecuritySELinuxRestoreSecurityFileLabel(const
>> char *path) }
>>
>> if (getContext(newpath, buf.st_mode, &fcon) < 0) { + /* Any user
>> created path likely does not have a default label, + * which
>> makes this an expected non error + */ VIR_WARN("cannot lookup
>> default selinux label for %s", newpath); + rc = 0;
>
> In the case where there is no default label to restore, shouldn't we still
> be removing our sVirt label rather than just ignoring the failure but
> leaving our label intact?
>

I don't know if we can just 'remove' a label, we have to replace it with a
different label, right? If I create a file under /mnt/foo the catch all label
is unconfined_u:object_r:file_t:s0 but not sure if we can hardcode that.

dwalsh, is there a way to programmatically determine the fallback default label?

- - Cole

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