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Check null stack to prevent heap-buffer-overflow #299

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Check null stack to prevent heap-buffer-overflow #299

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3 changes: 3 additions & 0 deletions src/api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1206,6 +1206,7 @@ yaml_document_add_scalar(yaml_document_t *document,

assert(document); /* Non-NULL document object is expected. */
assert(value); /* Non-NULL value is expected. */
if (STACK_NULL(&context, document->nodes)) goto error;

if (!tag) {
tag = (yaml_char_t *)YAML_DEFAULT_SCALAR_TAG;
Expand Down Expand Up @@ -1258,6 +1259,7 @@ yaml_document_add_sequence(yaml_document_t *document,
yaml_node_t node;

assert(document); /* Non-NULL document object is expected. */
if (STACK_NULL(&context, document->nodes)) goto error;
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@perlpunk perlpunk Jun 12, 2024 •
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I guess same the check would have to be added to yaml_document_add_scalar, yaml_document_add_mapping etc. to make this useful.

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Yes, there are other places needs stack checking. I saw your discussions and not sure this cve needs fix or not, just sending this patch to discuss. Will send a V2.


if (!tag) {
tag = (yaml_char_t *)YAML_DEFAULT_SEQUENCE_TAG;
Expand Down Expand Up @@ -1303,6 +1305,7 @@ yaml_document_add_mapping(yaml_document_t *document,
yaml_node_t node;

assert(document); /* Non-NULL document object is expected. */
if (STACK_NULL(&context, document->nodes)) goto error;

if (!tag) {
tag = (yaml_char_t *)YAML_DEFAULT_MAPPING_TAG;
Expand Down
5 changes: 5 additions & 0 deletions src/yaml_private.h
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Expand Up @@ -420,6 +420,11 @@ yaml_stack_extend(void **start, void **top, void **end);
YAML_DECLARE(int)
yaml_queue_extend(void **start, void **head, void **tail, void **end);

#define STACK_NULL(context,stack) \
(((stack).start != NULL) ? 0 : \
((context)->error = YAML_MEMORY_ERROR, \
1))

#define STACK_INIT(context,stack,type) \
(((stack).start = (type)yaml_malloc(INITIAL_STACK_SIZE*sizeof(*(stack).start))) ? \
((stack).top = (stack).start, \
Expand Down