fix(cjson_utils): add NULL check for cJSON_malloc in FindPointerFromObjectTo (#1049)

- Add missing NULL check for full_pointer allocation to prevent SIGSEGV on OOM.
- Free target_pointer and return NULL safely if full_pointer fails to allocate.
- Add oom_test unit test to verify graceful handling of memory allocation failure.

Signed-off-by: JIgar-maheshwari-dev <maheshwarijigar656@gmail.com>

Author: JIgar-maheshwari-dev

cJSON_Utils.c

@@ -203,6 +203,12 @@ CJSON_PUBLIC(char *) cJSONUtils_FindPointerFromObjectTo(const cJSON * const obje
             {
                 /* reserve enough memory for a 64 bit integer + '/' and '\0' */
                 unsigned char *full_pointer = (unsigned char*)cJSON_malloc(strlen((char*)target_pointer) + 20 + sizeof("/"));
+                if(full_pointer == NULL)
+                {
+                    /* Return early on allocation failure to prevent crash */
+                    cJSON_free(target_pointer);
+                    return NULL;
+                }
                 /* check if conversion to unsigned long is valid
                  * This should be eliminated at compile time by dead code elimination
                  * if size_t is an alias of unsigned long, or if it is bigger */
@@ -220,6 +226,12 @@ CJSON_PUBLIC(char *) cJSONUtils_FindPointerFromObjectTo(const cJSON * const obje
             if (cJSON_IsObject(object))
             {
                 unsigned char *full_pointer = (unsigned char*)cJSON_malloc(strlen((char*)target_pointer) + pointer_encoded_length((unsigned char*)current_child->string) + 2);
+                if(full_pointer == NULL)
+                {
+                    /* Return early on allocation failure to prevent crash */
+                    cJSON_free(target_pointer);
+                    return NULL;
+                }
                 full_pointer[0] = '/';
                 encode_string_as_pointer(full_pointer + 1, (unsigned char*)current_child->string);
                 strcat((char*)full_pointer, (char*)target_pointer);
@@ -1091,6 +1103,11 @@ static void compose_patch(cJSON * const patches, const unsigned char * const ope
         size_t suffix_length = pointer_encoded_length(suffix);
         size_t path_length = strlen((const char*)path);
         unsigned char *full_path = (unsigned char*)cJSON_malloc(path_length + suffix_length + sizeof("/"));
+        if(full_path == NULL)
+        {
+            /* Return early on allocation failure to prevent crash */
+            return;
+        }
 
         sprintf((char*)full_path, "%s/", (const char*)path);
         encode_string_as_pointer(full_path + path_length + 1, suffix);
@@ -1146,6 +1163,11 @@ static void create_patches(cJSON * const patches, const unsigned char * const pa
             cJSON *from_child = from->child;
             cJSON *to_child = to->child;
             unsigned char *new_path = (unsigned char*)cJSON_malloc(strlen((const char*)path) + 20 + sizeof("/")); /* Allow space for 64bit int. log10(2^64) = 20 */
+            if(new_path == NULL)
+            {
+                /* Return early on allocation failure to prevent crash */
+                return;
+            }
 
             /* generate patches for all array elements that exist in both "from" and "to" */
             for (index = 0; (from_child != NULL) && (to_child != NULL); (void)(from_child = from_child->next), (void)(to_child = to_child->next), index++)
@@ -1217,7 +1239,11 @@ static void create_patches(cJSON * const patches, const unsigned char * const pa
                     size_t path_length = strlen((const char*)path);
                     size_t from_child_name_length = pointer_encoded_length((unsigned char*)from_child->string);
                     unsigned char *new_path = (unsigned char*)cJSON_malloc(path_length + from_child_name_length + sizeof("/"));
-
+                    if(new_path == NULL)
+                    {
+                        /* Return early on allocation failure to prevent crash */
+                        return;
+                    }
                     sprintf((char*)new_path, "%s/", path);
                     encode_string_as_pointer(new_path + path_length + 1, (unsigned char*)from_child->string);
 

tests/CMakeLists.txt

@@ -93,7 +93,8 @@ if(ENABLE_CJSON_TEST)
         set (cjson_utils_tests
             json_patch_tests
             old_utils_tests
-            misc_utils_tests)
+            misc_utils_tests
+            oom_test)
 
         foreach (cjson_utils_test ${cjson_utils_tests})
             add_executable("${cjson_utils_test}" "${cjson_utils_test}.c")

tests/oom_test.c

@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "unity/examples/unity_config.h"
+#include "unity/src/unity.h"
+#include "../cJSON.h"
+#include "../cJSON_Utils.h"
+#include "common.h"
+
+static int g_alloc_count = 0;
+static int g_fail_at = -1;
+
+/* Custom malloc hook to simulate OOM on a specific allocation */
+static void* failing_malloc(size_t size)
+{
+    int idx = g_alloc_count++;
+    if (idx == g_fail_at)
+    {
+        return NULL; /* Simulate allocation failure */
+    }
+    return malloc(size);
+}
+
+void setUp(void)
+{
+    /* Declare variables at top of block */
+    cJSON_Hooks hooks;
+
+    hooks.malloc_fn = failing_malloc;
+    hooks.free_fn = free;
+
+    g_alloc_count = 0;
+    g_fail_at = -1;
+
+    /* Register custom memory hook */
+    cJSON_InitHooks(&hooks);
+}
+
+void tearDown(void)
+{
+    /* Reset hooks back to default */
+    cJSON_InitHooks(NULL);
+}
+
+static void find_pointer_should_handle_null_on_oom(void)
+{
+    /* 1. ALL variable declarations MUST be at the very top */
+    cJSON *root = NULL;
+    cJSON *inner = NULL;
+    cJSON *target = NULL;
+    char *pointer = NULL;
+
+    /* 2. Executable code starts here */
+    root = cJSON_CreateArray();
+    inner = cJSON_CreateArray();
+    cJSON_AddItemToArray(root, inner);
+
+    target = cJSON_CreateNumber(42);
+    cJSON_AddItemToArray(inner, target);
+
+    /* Reset alloc counter right before calling FindPointer */
+    g_alloc_count = 0;
+    g_fail_at = 1;
+
+    pointer = cJSONUtils_FindPointerFromObjectTo(root, target);
+
+    /* Assertion */
+    TEST_ASSERT_NULL(pointer);
+
+    /* Cleanup memory */
+    cJSON_Delete(root);
+}
+
+int CJSON_CDECL main(void)
+{
+    UNITY_BEGIN();
+
+    RUN_TEST(find_pointer_should_handle_null_on_oom);
+
+    return UNITY_END();
+}