From a03d649a488db32f1842885dbae1bf1926e2957b Mon Sep 17 00:00:00 2001
From: "Wladimir J. van der Laan" <laanwj@gmail.com>
Date: Thu, 3 May 2018 12:53:32 +0200
Subject: [PATCH] Merge #13148: logging: Fix potential use-after-free in
 LogPrintStr(...)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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 | 17 ++++++++---------
 src/logging.h   |  2 +-
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/src/logging.cpp b/src/logging.cpp
index 5cde0f6324..f8fa4ed6e1 100644
--- a/src/logging.cpp
+++ b/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);
 
@@ -261,7 +259,7 @@ 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) {
@@ -269,7 +267,6 @@ int BCLog::Logger::LogPrintStr(const std::string &str)
 
         // buffer if we haven't opened the log yet
         if (m_fileout == nullptr) {
-            ret = strTimestamped.length();
             m_msgs_before_open.push_back(strTimestamped);
         }
         else
@@ -277,14 +274,16 @@ int BCLog::Logger::LogPrintStr(const std::string &str)
             // 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()
diff --git a/src/logging.h b/src/logging.h
index da4b4208fe..1d08ca1cad 100644
--- a/src/logging.h
+++ b/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; }