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qapi: change QmpInputVisitor to QSLIST

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This saves a lot of memory compared to a statically-sized array,
or at least 24kb could be considered a lot on an Atari ST.
It also makes the code more similar to QmpOutputVisitor.

This removes the limit on the depth of a QObject that can be processed
into a QAPI tree. This is not a problem because QObjects can be
considered trusted; the text received on the QMP wire is untrusted
input, but the JSON parser already takes pains to limit the QObject tree
it creates. We don't need the QMP input visitor to limit it again.

Backports commit 3d344c2aabb7bc9b414321e3c52872901edebdda from qemu
This commit is contained in:
Paolo Bonzini 2018-02-25 20:02:01 -05:00 committed by Lioncash
parent b14f1d7a80
commit 674805745b
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 29 additions and 28 deletions
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57
qemu/qapi/qmp-input-visitor.c
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@ -29,6 +29,8 @@ typedef struct StackObject
GHashTable *h; /* If obj is dict: unvisited keys */ GHashTable *h; /* If obj is dict: unvisited keys */
const QListEntry *entry; /* If obj is list: unvisited tail */ const QListEntry *entry; /* If obj is list: unvisited tail */
QSLIST_ENTRY(StackObject) node;
} StackObject; } StackObject;
struct QmpInputVisitor struct QmpInputVisitor
@ -40,8 +42,7 @@ struct QmpInputVisitor
/* Stack of objects being visited (all entries will be either /* Stack of objects being visited (all entries will be either
* QDict or QList). */ * QDict or QList). */
StackObject stack[QIV_STACK_SIZE]; QSLIST_HEAD(, StackObject) stack;
int nb_stack;
/* True to reject parse in visit_end_struct() if unvisited keys remain. */ /* True to reject parse in visit_end_struct() if unvisited keys remain. */
bool strict; bool strict;
@ -60,13 +61,13 @@ static QObject *qmp_input_get_object(QmpInputVisitor *qiv,
QObject *qobj; QObject *qobj;
QObject *ret; QObject *ret;
if (!qiv->nb_stack) { if (QSLIST_EMPTY(&qiv->stack)) {
/* Starting at root, name is ignored. */ /* Starting at root, name is ignored. */
return qiv->root; return qiv->root;
} }
/* We are in a container; find the next element. */ /* We are in a container; find the next element. */
tos = &qiv->stack[qiv->nb_stack - 1]; tos = QSLIST_FIRST(&qiv->stack);
qobj = tos->obj; qobj = tos->obj;
assert(qobj); assert(qobj);
@ -99,18 +100,12 @@ static const QListEntry *qmp_input_push(QmpInputVisitor *qiv, QObject *obj,
void *qapi, Error **errp) void *qapi, Error **errp)
{ {
GHashTable *h; GHashTable *h;
StackObject *tos = &qiv->stack[qiv->nb_stack]; StackObject *tos = g_new0(StackObject, 1);
assert(obj); assert(obj);
if (qiv->nb_stack >= QIV_STACK_SIZE) {
error_setg(errp, "An internal buffer overran");
return NULL;
}
tos->obj = obj; tos->obj = obj;
tos->qapi = qapi; tos->qapi = qapi;
assert(!tos->h);
assert(!tos->entry);
if (qiv->strict && qobject_type(obj) == QTYPE_QDICT) { if (qiv->strict && qobject_type(obj) == QTYPE_QDICT) {
h = g_hash_table_new(g_str_hash, g_str_equal); h = g_hash_table_new(g_str_hash, g_str_equal);
@ -120,7 +115,7 @@ static const QListEntry *qmp_input_push(QmpInputVisitor *qiv, QObject *obj,
tos->entry = qlist_first(qobject_to_qlist(obj)); tos->entry = qlist_first(qobject_to_qlist(obj));
} }
qiv->nb_stack++; QSLIST_INSERT_HEAD(&qiv->stack, tos, node);
return tos->entry; return tos->entry;
} }
@ -134,9 +129,9 @@ static gboolean always_true(gpointer key, gpointer val, gpointer user_pkey)
static void qmp_input_check_struct(Visitor *v, Error **errp) static void qmp_input_check_struct(Visitor *v, Error **errp)
{ {
QmpInputVisitor *qiv = to_qiv(v); QmpInputVisitor *qiv = to_qiv(v);
StackObject *tos = &qiv->stack[qiv->nb_stack - 1]; StackObject *tos = QSLIST_FIRST(&qiv->stack);
assert(qiv->nb_stack > 0); assert(tos && !tos->entry);
if (qiv->strict) { if (qiv->strict) {
GHashTable *const top_ht = tos->h; GHashTable *const top_ht = tos->h;
@ -150,23 +145,23 @@ static void qmp_input_check_struct(Visitor *v, Error **errp)
} }
} }
static void qmp_input_stack_object_free(StackObject *tos)
{
if (tos->h) {
g_hash_table_unref(tos->h);
}
g_free(tos);
}
static void qmp_input_pop(Visitor *v, void **obj) static void qmp_input_pop(Visitor *v, void **obj)
{ {
QmpInputVisitor *qiv = to_qiv(v); QmpInputVisitor *qiv = to_qiv(v);
StackObject *tos = &qiv->stack[qiv->nb_stack - 1]; StackObject *tos = QSLIST_FIRST(&qiv->stack);
assert(qiv->nb_stack > 0); assert(tos && tos->qapi == obj);
assert(tos->qapi == obj); QSLIST_REMOVE_HEAD(&qiv->stack, node);
qmp_input_stack_object_free(tos);
if (qiv->strict) {
GHashTable * const top_ht = qiv->stack[qiv->nb_stack - 1].h;
if (top_ht) {
g_hash_table_unref(top_ht);
}
tos->h = NULL;
}
qiv->nb_stack--;
} }
static void qmp_input_start_struct(Visitor *v, const char *name, void **obj, static void qmp_input_start_struct(Visitor *v, const char *name, void **obj,
@ -226,7 +221,7 @@ static GenericList *qmp_input_next_list(Visitor *v, GenericList *tail,
size_t size) size_t size)
{ {
QmpInputVisitor *qiv = to_qiv(v); QmpInputVisitor *qiv = to_qiv(v);
StackObject *so = &qiv->stack[qiv->nb_stack - 1]; StackObject *so = QSLIST_FIRST(&qiv->stack);
if (!so->entry) { if (!so->entry) {
return NULL; return NULL;
@ -377,6 +372,12 @@ static void qmp_input_optional(Visitor *v, const char *name, bool *present)
static void qmp_input_free(Visitor *v) static void qmp_input_free(Visitor *v)
{ {
QmpInputVisitor *qiv = to_qiv(v); QmpInputVisitor *qiv = to_qiv(v);
while (!QSLIST_EMPTY(&qiv->stack)) {
StackObject *tos = QSLIST_FIRST(&qiv->stack);
QSLIST_REMOVE_HEAD(&qiv->stack, node);
qmp_input_stack_object_free(tos);
}
qobject_decref(qiv->root); qobject_decref(qiv->root);
g_free(qiv); g_free(qiv);