From: virtiofs-bot@sinrega.org
To: virtio-fs@redhat.com
Subject: [Virtio-fs] [virtiofsd] MR merged: keep `DAC_OVERRIDE` after changing the uid/gid
Date: Thu, 1 Dec 2022 06:30:37 +0000 (UTC) [thread overview]
Message-ID: <41652.122120101303500517@us-mta-367.us.mimecast.lan> (raw)
Currently, the FUSE protocol doesn't send the process supplementary
groups. This causes some use cases to fail, for instance
(user belongs to "wheel"):
# mkdir -m 0770 testdir
# chgrp wheel testdir
# su user -c "touch testdir/file"
it should succeed but fails with "Permission denied".
The Kata team also reported a database init failure due to lack of
support of supplementary groups:
"kata database failed due to permission issue in mssql/mariadb/pssql:
cannot create directory '/var/lib/mysql/data': Permission denied"
Although the actual solution requires a modification of the FUSE
protocol, and Miklos is working on a solution. In the meantime,
to work around this, we can set the `DAC_OVERRIDE` in the effective set
after changing the credentials. We are allowed to set the capability
because we only change the effective user ID, so we still have the
'DAC_OVERRIDE' in the permitted set.
An alternative workaround is to set `SECBIT_NO_SETUID_FIXUP` to avoid
clearing the caps effective set, but it has the disadvantage that we
must be careful and drop `FSETID` (and probably a few others) or we
risk introducing some security bugs, like CVE-2022-0358 [0].
The biggest drawback of this workaround, it will not work on top of
NFS (and probably also CEPH) and might be limited to local
filesystems.
[0] https://gitlab.com/virtio-fs/virtiofsd/-/merge_requests/77
This is a workaround for #59
closes #30
---
https://gitlab.com/virtio-fs/virtiofsd/-/merge_requests/142
reply other threads:[~2022-12-01 6:30 UTC|newest]
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