From 5ad8e9140621a9a035270a96a1e0ad0750d5483a Mon Sep 17 00:00:00 2001
From: Bryan Call <bcall@apache.org>
Date: Thu, 11 Dec 2025 15:12:17 -0800
Subject: [PATCH] Fix null pointer dereference in traffic_crashlog

ServerBacktrace() can return 0 (success) but leave the trace pointer
null when the target process has already exited. This caused a SEGV
when fprintf() was called with the null trace pointer.

Add a null check before using the trace pointer.
---
 src/traffic_crashlog/traffic_crashlog.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/traffic_crashlog/traffic_crashlog.cc b/src/traffic_crashlog/traffic_crashlog.cc
index 65eee7bc50b..9354c5f838c 100644
--- a/src/traffic_crashlog/traffic_crashlog.cc
+++ b/src/traffic_crashlog/traffic_crashlog.cc
@@ -109,6 +109,11 @@ crashlog_write_backtrace(FILE *fp, pid_t pid, const crashlog_target &)
     return false;
   }
 
+  if (trace == nullptr) {
+    fprintf(fp, "Unable to retrieve backtrace: trace is null\n");
+    return false;
+  }
+
   fprintf(fp, "%s", trace);
   free(trace);
   return true;