block: Fix -blockdev for certain non-string scalars

Configuration flows through the block subsystem in a rather peculiar
way.  Configuration made with -drive enters it as QemuOpts.
Configuration made with -blockdev / blockdev-add enters it as QAPI
type BlockdevOptions.  The block subsystem uses QDict, QemuOpts and
QAPI types internally.  The precise flow is next to impossible to
explain (I tried for this commit message, but gave up after wasting
several hours).  What I can explain is a flaw in the BlockDriver
interface that leads to this bug:

    $ qemu-system-x86_64 -blockdev node-name=n1,driver=nfs,server.type=inet,server.host=localhost,path=/foo/bar,user=1234
    qemu-system-x86_64: -blockdev node-name=n1,driver=nfs,server.type=inet,server.host=localhost,path=/foo/bar,user=1234: Internal error: parameter user invalid

QMP blockdev-add is broken the same way.

Here's what happens.  The block layer passes configuration represented
as flat QDict (with dotted keys) to BlockDriver methods
.bdrv_file_open().  The QDict's members are typed according to the
QAPI schema.

nfs_file_open() converts it to QAPI type BlockdevOptionsNfs, with
qdict_crumple() and a qobject input visitor.

This visitor comes in two flavors.  The plain flavor requires scalars
to be typed according to the QAPI schema.  That's the case here.  The
keyval flavor requires string scalars.  That's not the case here.
nfs_file_open() uses the latter, and promptly falls apart for members
@user, @group, @tcp-syn-count, @readahead-size, @page-cache-size,
@debug.

Switching to the plain flavor would fix -blockdev, but break -drive,
because there the scalars arrive in nfs_file_open() as strings.

The proper fix would be to replace the QDict by QAPI type
BlockdevOptions in the BlockDriver interface.  Sadly, that's beyond my
reach right now.

Next best would be to fix the block layer to always pass correctly
typed QDicts to the BlockDriver methods.  Also beyond my reach.

What I can do is throw another hack onto the pile: have
nfs_file_open() convert all members to string, so use of the keyval
flavor actually works, by replacing qdict_crumple() by new function
qdict_crumple_for_keyval_qiv().

The pattern "pass result of qdict_crumple() to
qobject_input_visitor_new_keyval()" occurs several times more:

* qemu_rbd_open()

  Same issue as nfs_file_open(), but since BlockdevOptionsRbd has only
  string members, its only a latent bug.  Fix it anyway.

* parallels_co_create_opts(), qcow_co_create_opts(),
  qcow2_co_create_opts(), bdrv_qed_co_create_opts(),
  sd_co_create_opts(), vhdx_co_create_opts(), vpc_co_create_opts()

  These work, because they create the QDict with
  qemu_opts_to_qdict_filtered(), which creates only string scalars.
  The function sports a TODO comment asking for better typing; that's
  going to be fun.  Use qdict_crumple_for_keyval_qiv() to be safe.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/qobject/block-qdict.c b/qobject/block-qdict.c
index fb92010dc5..aba372c2eb 100644
--- a/qobject/block-qdict.c
+++ b/qobject/block-qdict.c
@@ -9,7 +9,10 @@
 
 #include "qemu/osdep.h"
 #include "block/qdict.h"
+#include "qapi/qmp/qbool.h"
 #include "qapi/qmp/qlist.h"
+#include "qapi/qmp/qnum.h"
+#include "qapi/qmp/qstring.h"
 #include "qemu/cutils.h"
 #include "qapi/error.h"
 
@@ -514,6 +517,60 @@ QObject *qdict_crumple(const QDict *src, Error **errp)
 }
 
 /**
+ * qdict_crumple_for_keyval_qiv:
+ * @src: the flat dictionary (only scalar values) to crumple
+ * @errp: location to store error
+ *
+ * Like qdict_crumple(), but additionally transforms scalar values so
+ * the result can be passed to qobject_input_visitor_new_keyval().
+ *
+ * The block subsystem uses this function to prepare its flat QDict
+ * with possibly confused scalar types for a visit.  It should not be
+ * used for anything else, and it should go away once the block
+ * subsystem has been cleaned up.
+ */
+QObject *qdict_crumple_for_keyval_qiv(QDict *src, Error **errp)
+{
+    QDict *tmp = NULL;
+    char *buf;
+    const char *s;
+    const QDictEntry *ent;
+    QObject *dst;
+
+    for (ent = qdict_first(src); ent; ent = qdict_next(src, ent)) {
+        buf = NULL;
+        switch (qobject_type(ent->value)) {
+        case QTYPE_QNULL:
+        case QTYPE_QSTRING:
+            continue;
+        case QTYPE_QNUM:
+            s = buf = qnum_to_string(qobject_to(QNum, ent->value));
+            break;
+        case QTYPE_QDICT:
+        case QTYPE_QLIST:
+            /* @src isn't flat; qdict_crumple() will fail */
+            continue;
+        case QTYPE_QBOOL:
+            s = qbool_get_bool(qobject_to(QBool, ent->value))
+                ? "on" : "off";
+            break;
+        default:
+            abort();
+        }
+
+        if (!tmp) {
+            tmp = qdict_clone_shallow(src);
+        }
+        qdict_put(tmp, ent->key, qstring_from_str(s));
+        g_free(buf);
+    }
+
+    dst = qdict_crumple(tmp ?: src, errp);
+    qobject_unref(tmp);
+    return dst;
+}
+
+/**
  * qdict_array_entries(): Returns the number of direct array entries if the
  * sub-QDict of src specified by the prefix in subqdict (or src itself for
  * prefix == "") is valid as an array, i.e. the length of the created list if