Avoid remapping freed memory in trace sender fallback

Signed-off-by: Bob Weinand <bob.weinand@datadoghq.com>
DataDog · Feb 28, 2024 · 7c3beba · 7c3beba
1 parent b436003
commit 7c3beba
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Showing 2 changed files with 9 additions and 5 deletions.
diff --git a/ext/auto_flush.c b/ext/auto_flush.c
@@ -70,10 +70,14 @@ ZEND_RESULT_CODE ddtrace_flush_tracer(bool force_on_startup, bool collect_cycles
                         do {
                             if (send_error.tag == DDOG_OPTION_VEC_U8_SOME_VEC_U8) {
                                 // retry sending it directly through the socket as last resort. May block though with large traces.
-                                ddog_map_shm(shm, &mapped_shm, &ptr, &size);
-                                ddog_MaybeError retry_error = ddog_sidecar_send_trace_v04_bytes(&ddtrace_sidecar, ddtrace_sidecar_instance_id, (ddog_CharSlice){ .ptr = ptr, .len = size }, &tags);
-                                shm = ddog_unmap_shm(mapped_shm);
-                                ddog_drop_anon_shm_handle(shm);
+                                ptr = emalloc(written);
+                                // write the same thing again
+                                ddtrace_serialize_simple_array_into_mapped_menory(&traces, ptr, written);
+
+                                ddog_MaybeError retry_error = ddog_sidecar_send_trace_v04_bytes(&ddtrace_sidecar, ddtrace_sidecar_instance_id, (ddog_CharSlice){ .ptr = ptr, .len = written }, &tags);
+
+                                efree(ptr);
+
                                 if (ddtrace_ffi_try("Failed sending traces to the sidecar", retry_error)) {
                                     LOG(DEBUG, "Failed sending traces via shm to sidecar: %.*s", (int) send_error.some.len, send_error.some.ptr);
                                 } else {

diff --git a/ext/serializer.c b/ext/serializer.c
@@ -179,7 +179,7 @@ size_t ddtrace_serialize_simple_array_into_mapped_menory(zval *trace, char *map,
         mpack_writer_destroy(&writer);
         return 0;
     }
-    size_t written = mpack_writer_buffer_size(&writer);
+    size_t written = mpack_writer_buffer_used(&writer);
     // finish writing
     if (mpack_writer_destroy(&writer) != mpack_ok) {
         return 0;