Clear log if invalid

lib/Logging/Logging.cpp

@@ -80,10 +80,12 @@ std::string getLastLogs() {
   return output;
 }
 
-void sanitizeLogHead() {
+bool sanitizeLogHead() {
   if (logHead >= MAX_LOG_LINES) {
     logHead = 0;
+    return true;
   }
+  return false;
 }
 
 void clearLastLogs() {

lib/Logging/Logging.h

@@ -57,9 +57,11 @@ void logPrintf(const char* level, const char* origin, const char* format, ...);
 
 std::string getLastLogs();
 void clearLastLogs();
-// Clamps logHead into range without wiping messages — safe to call on panic
-// reboots where the panic occurred before begin() ever had a chance to run.
-void sanitizeLogHead();
+// Clamps logHead into range. Returns true if logHead was out of range (repaired),
+// which also means logMessages is untrusted garbage. Callers should call
+// clearLastLogs() when this returns true so getLastLogs() does not dump corrupt
+// data into crash reports.
+bool sanitizeLogHead();
 
 class MySerialImpl : public Print {
  public:

lib/hal/HalSystem.cpp

@@ -79,7 +79,11 @@ void begin() {
   } else {
     // Panic reboot: preserve logs and panic info, but clamp logHead in case the
     // panic occurred before begin() ever ran (e.g. in a static constructor).
-    sanitizeLogHead();
+    // If logHead was out of range, logMessages is also garbage — clear it so
+    // getLastLogs() does not dump corrupt data into the crash report.
+    if (sanitizeLogHead()) {
+      clearLastLogs();
+    }
   }
 }