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Thu, 10 Sep 2020 18:38:48 +0000 (UTC) Date: Thu, 10 Sep 2020 19:38:46 +0100 From: "Dr. David Alan Gilbert" To: =?iso-8859-1?B?SuFu?= Tomko Subject: Re: [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option Message-ID: <20200910183846.GO2814@work-vm> References: <20200827153657.111098-1-dgilbert@redhat.com> <20200827153657.111098-4-dgilbert@redhat.com> <20200909112012.GD1377607@lpt> MIME-Version: 1.0 In-Reply-To: <20200909112012.GD1377607@lpt> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/10 09:07:44 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Ján Tomko (jtomko@redhat.com) wrote: > On a Thursday in 2020, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" > > > > Add an option to define mappings of xattr names so that > > the client and server filesystems see different views. > > This can be used to have different SELinux mappings as > > seen by the guest, to run the virtiofsd with less privileges > > (e.g. in a case where it can't set trusted/system/security > > xattrs but you want the guest to be able to), or to isolate > > multiple users of the same name; e.g. trusted attributes > > used by stacking overlayfs. > > > > A mapping engine is used wit 3 simple rules; the rules can > > be combined to allow most useful mapping scenarios. > > The ruleset is defined by -o xattrmap='rules...'. > > > > This patch doesn't use the rule maps yet. > > > > Signed-off-by: Dr. David Alan Gilbert > > --- > > docs/tools/virtiofsd.rst | 55 ++++++++++++ > > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++ > > 2 files changed, 203 insertions(+) > > > > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst > > index 824e713491..2efa16d3c5 100644 > > --- a/docs/tools/virtiofsd.rst > > +++ b/docs/tools/virtiofsd.rst > > @@ -107,6 +107,60 @@ Options > > performance. ``auto`` acts similar to NFS with a 1 second metadata cache > > timeout. ``always`` sets a long cache lifetime at the expense of coherency. > > > > +xattr-mapping > > +------------- > > + > > +By default the name of xattr's used by the client are passed through to the server > > +file system. This can be a problem where either those xattr names are used > > +by something on the server (e.g. selinux client/server confusion) or if the > > +virtiofsd is running in a container with restricted priviliges where it cannot > > privileges Fixed. > > +access some attributes. > > + > > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping`` > > +string consists of a series of rules. > > + > > +The first matching rule terminates the mapping. > > + > > +Each rule consists of a number of fields separated with a separator that is the > > +first non-white space character in the rule. This separator must then be used > > +for the whole rule. > > +White space may be added before and after each rule. > > +Using ':' as the separator a rule is of the form: > > + > > +``:scope:type:key:prepend:`` > > + > > +**scope** is: > > + > > +- 'client' - match 'key' against a xattr name from the client for > > + setxattr/getxattr/removexattr > > +- 'server' - match 'prepend' against a xattr name from the server > > + for listxattr > > +- 'all' - can be used to match both cases. > > + > > +**type** is one of: > > + > > +- 'prefix' - If 'key' matches the client then the 'prepend' > > + is added before the name is passed to the server. > > + For a server case, the prepend is tested and stripped > > + if matching. > > + > > +- 'ok' - The attribute name is OK and passed through to > > + the server unchanged. > > + > > +- 'bad' - If a client tries to use this name it's > > + denied using EPERM; when the server passes an attribute > > + name matching it's hidden. > > + > > +**key** is a string tested as a prefix on an attribute name originating > > +on the client. It maybe empty in which case a 'client' rule > > +will always match on client names. > > + > > +**prepend** is a string tested as a prefix on an attribute name originiating > > originating Done. > > +on the server, and used as a new prefix. It maybe empty > > may be OK > > +in which case a 'server' rule will always match on all names from > > +the server. > > + > > + > > Examples > > -------- > > > > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket > > -numa node,memdev=mem \ > > ... > > guest# mount -t virtiofs myfs /mnt > > + > > git complains about trailing whitespace at EOF Eaten. Dave > Jano -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK