Merge bitcoin#13148: logging: Fix potential use-after-free in LogPrin…

…tStr(...)

0bd4cd3 logging: remove unused return value from LogPrintStr (practicalswift)
76f344d logging: Fix potential use-after-free in LogPrintStr(...) (practicalswift)

Pull request description:

  Fix potential use-after-free in `LogPrintStr(...)`.

  `freopen(…)` frees `m_fileout`.

Tree-SHA512: ceee1f659c10a21525aa648377afeea0a37016339f5269dea54850ba3b475aa316f4931081655717b65f981598fdc9d79a1e79e55f7084c242eeb7bf372bc4b6

src/logging.cpp

@@ -247,10 +247,8 @@ std::string BCLog::Logger::LogThreadNameStr(const std::string &str)
     return strThreadLogged;
 }
 
-int BCLog::Logger::LogPrintStr(const std::string &str)
+void BCLog::Logger::LogPrintStr(const std::string &str)
 {
-    int ret = 0; // Returns total number of characters written
-
     std::string strThreadLogged = LogThreadNameStr(str);
     std::string strTimestamped = LogTimestampStr(strThreadLogged);
 
@@ -261,30 +259,31 @@ int BCLog::Logger::LogPrintStr(const std::string &str)
 
     if (m_print_to_console) {
         // print to console
-        ret = fwrite(strTimestamped.data(), 1, strTimestamped.size(), stdout);
+        fwrite(strTimestamped.data(), 1, strTimestamped.size(), stdout);
         fflush(stdout);
     }
     if (m_print_to_file) {
         std::lock_guard<std::mutex> scoped_lock(m_file_mutex);
 
         // buffer if we haven't opened the log yet
         if (m_fileout == nullptr) {
-            ret = strTimestamped.length();
             m_msgs_before_open.push_back(strTimestamped);
         }
         else
         {
             // reopen the log file, if requested
             if (m_reopen_file) {
                 m_reopen_file = false;
-                if (fsbridge::freopen(m_file_path,"a",m_fileout) != nullptr)
-                    setbuf(m_fileout, nullptr); // unbuffered
+                m_fileout = fsbridge::freopen(m_file_path, "a", m_fileout);
+                if (!m_fileout) {
+                    return;
+                }
+                setbuf(m_fileout, nullptr); // unbuffered
             }
 
-            ret = FileWriteStr(strTimestamped, m_fileout);
+            FileWriteStr(strTimestamped, m_fileout);
         }
     }
-    return ret;
 }
 
 void BCLog::Logger::ShrinkDebugFile()

src/logging.h

@@ -111,7 +111,7 @@ namespace BCLog {
         std::atomic<bool> m_reopen_file{false};
 
         /** Send a string to the log output */
-        int LogPrintStr(const std::string &str);
+        void LogPrintStr(const std::string &str);
 
         /** Returns whether logs will be written to any output */
         bool Enabled() const { return m_print_to_console || m_print_to_file; }