apr_buffer_cpy: return NULL on allocation failure to avoid undefined behaviour

buffer/apr_buffer.c

@@ -297,6 +297,9 @@ APR_DECLARE(apr_buffer_t *) apr_buffer_cpy(apr_buffer_t *dst,
         apr_size_t size = src->size + src->zero_terminated;
 
         void *mem = alloc(ctx, size);
+        if (!mem) {
+            return NULL;
+        }
         memcpy(mem, src->d.mem, size);
 
         dst->zero_terminated = src->zero_terminated;

include/apr_buffer.h

@@ -354,7 +354,7 @@ APR_DECLARE(apr_status_t) apr_buffer_dup(apr_buffer_t **out,
  * @param src The second buffer
  * @param alloc The function callback to allocate memory for the buffer
  * @param ctx The context for the callback
- * @return Returns dst.
+ * @return Returns dst, or NULL if alloc is provided and returns NULL.
  */
 APR_DECLARE(apr_buffer_t *) apr_buffer_cpy(apr_buffer_t *dst,
                                            const apr_buffer_t *src,

test/testbuffer.c

@@ -265,6 +265,22 @@ static void test_compare_buffers(abts_case *tc, void *data)
     apr_pool_destroy(pool);
 }
 
+static void *test_failing_alloc(void *ctx, apr_size_t size)
+{
+    return NULL;
+}
+
+static void test_buffer_cpy_alloc_failure(abts_case *tc, void *data)
+{
+    apr_buffer_t src, dst;
+
+    apr_buffer_str_set(&src, "test", APR_BUFFER_STRING);
+    memset(&dst, 0, sizeof(dst));
+
+    ABTS_ASSERT(tc, "apr_buffer_cpy returns NULL on alloc failure",
+                    apr_buffer_cpy(&dst, &src, test_failing_alloc, NULL) == NULL);
+}
+
 abts_suite *testbuffer(abts_suite *suite)
 {
     suite = ADD_SUITE(suite);
@@ -274,6 +290,7 @@ abts_suite *testbuffer(abts_suite *suite)
     abts_run_test(suite, test_null_buffer, NULL);
     abts_run_test(suite, test_buffers, NULL);
     abts_run_test(suite, test_compare_buffers, NULL);
+    abts_run_test(suite, test_buffer_cpy_alloc_failure, NULL);
 
     return suite;
 }