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virsh: snapshot: Don't validate schema of XML generated by 'virsh snapshot-create-as'

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Commit 95f8e3237e which introduced XML schema validation
for snapshot XMLs always asserted the validation for the XML generated
by 'virsh snapshot-create-as' on the basis that it's libvirt-generated,
thus valid.

This unfortunately isn't true as users can influence certain bits of the
XML such as the disk image path which must be a full path. Thus if a
user tries to invoke virsh as:

 $ virsh snapshot-create-as upstream --diskspec vda,file=relative.qcow2
 error: XML document failed to validate against schema: Unable to validate doc against /path/to/domainsnapshot.rng
 Extra element disks in interleave
 Element domainsnapshot failed to validate content

They get a rather useless error from the libxml2 RNG validator.

With this fix applied, we get to the XML parser in libvirtd which has a
more reasonable error:

 $ virsh snapshot-create-as upstream --diskspec vda,file=relative.qcow2
 error: XML error: disk snapshot image path 'relative.qcow2' must be absolute

Instead users can force validation of the XML generated by 'virsh
snapshot-create-as' by passing the '--validate' flag.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
This commit is contained in:
Peter Krempa 2021-04-15 13:26:37 +02:00
parent f0379bdd14
commit f1c9fed2ca
2 changed files with 10 additions and 2 deletions
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4
docs/manpages/virsh.rst
View File

@ -6916,7 +6916,7 @@ snapshot-create-as
snapshot-create-as domain {[--print-xml] [--no-metadata]
[--halt] [--reuse-external]} [name]
[description] [--disk-only [--quiesce]] [--atomic]
[description] [--disk-only [--quiesce]] [--atomic] [--validate]
[[--live] [--memspec memspec]] [--diskspec] diskspec]...
Create a snapshot for domain *domain* with the given <name> and
@ -6988,6 +6988,8 @@ For now, it is not possible to create snapshots in a domain that has
checkpoints, although this restriction will be lifted in a future
release.
Optionally, the *--validate* option can be passed to validate XML document
which is internally generated by this command against the internal RNG schema.
snapshot-current
----------------

8
tools/virsh-snapshot.c
View File

@ -372,6 +372,10 @@ static const vshCmdOptDef opts_snapshot_create_as[] = {
.help = N_("require atomic operation")
},
VIRSH_COMMON_OPT_LIVE(N_("take a live snapshot")),
{.name = "validate",
.type = VSH_OT_BOOL,
.help = N_("validate the XML against the schema"),
},
{.name = "memspec",
.type = VSH_OT_STRING,
.flags = VSH_OFLAG_REQ_OPT,
@ -394,7 +398,7 @@ cmdSnapshotCreateAs(vshControl *ctl, const vshCmd *cmd)
const char *desc = NULL;
const char *memspec = NULL;
g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
unsigned int flags = VIR_DOMAIN_SNAPSHOT_CREATE_VALIDATE;
unsigned int flags = 0;
const vshCmdOpt *opt = NULL;
if (vshCommandOptBool(cmd, "no-metadata"))
@ -411,6 +415,8 @@ cmdSnapshotCreateAs(vshControl *ctl, const vshCmd *cmd)
flags |= VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC;
if (vshCommandOptBool(cmd, "live"))
flags |= VIR_DOMAIN_SNAPSHOT_CREATE_LIVE;
if (vshCommandOptBool(cmd, "validate"))
flags |= VIR_DOMAIN_SNAPSHOT_CREATE_VALIDATE;
if (!(dom = virshCommandOptDomain(ctl, cmd, NULL)))
return false;