Re: lsetxattr failed, SELINUX_ERR op=setxattr invalid_context

On Wed, Feb 9, 2022 at 12:16 AM Chris Murphy <[email protected]>
wrote:

> Hi,
>
> I'm running Fedora 35, and I'm trying to replicate a Fedora 36 root
> snapshot from one Btrfs file system to another, but it fails.
>
> This is what I see on CLI (with verbose logging)
>
> set_xattr etc/NetworkManager/dispatcher.d - name=security.selinux
> data_len=56 data=system_u:object_r:NetworkManager_dispatcher_script_t:s0
> ERROR: lsetxattr etc/NetworkManager/dispatcher.d
> security.selinux=system_u:object_r:NetworkManager_dispatcher_script_t:s0
> failed: Invalid argument
>
> This is the AVC error:
>
> [25325.074972] audit[23509]: AVC avc:  denied  { mac_admin } for
> pid=23509 comm="btrfs" capability=33
> scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
> tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
> tclass=capability2 permissive=0
> [25325.075188] audit: SELINUX_ERR op=setxattr
> invalid_context="system_u:object_r:NetworkManager_dispatcher_script_t:s0"
>
>
> I think what's going on is, Fedora 35's SELinux is preventing `btrfs
> receive` from setting a label it doesn't know. If so, is this definitely
> the correct behavior? Or is there something `btrfs receive`
> could do to allow setting this unfamiliar label anyway, or is this an
> unacceptable risk to set arbitrary labels?
>
Hi,

I cannot speak for btrfs, but from SELinux PoV this seems to be correct:
When a file is restored including extended attributes and the SELinux type
is not known, it should fail, probably unlabeled_t will be seen there. If
there is no better solution, I'd go with not setting labels at all and
restore them later using

fixfiles onboot -F



>
> I filed a btrfs-progs bug, feel free to answer there (or here)
> https://github.com/kdave/btrfs-progs/issues/447
>
> Thanks,
>
> --
> Chris Murphy
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-- 

Zdenek Pytela
Security SELinux team

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