Fix a condition in utilities::logger::append_newline

The previous condition assumes enough space to append an extra newline followed by \0. If we already have a full message buffer, appending would overflow and the \0 would corrupt some adjacent variable. If this adjacent variable happens to be the guard from the calling function, it would be corrupted and fails to unlock its lock, causing other logging components to stuck forever waiting for that lock.
rubinius · Feb 24, 2016 · 0b4b712 · 0b4b712
1 parent 928f49b
commit 0b4b712
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/vm/util/logger.cpp b/vm/util/logger.cpp
@@ -54,7 +54,7 @@ namespace rubinius {
         char* end = (char*)memchr(message, '\0', LOGGER_MSG_SIZE);
         size_t bytes = end ? end - message : LOGGER_MSG_SIZE;
 
-        if(bytes < LOGGER_MSG_SIZE) {
+        if(LOGGER_MSG_SIZE - bytes > 1) {
           if(message[bytes-1] != '\n') {
             message[bytes] = '\n';
             message[bytes += 1] = '\0';