The fix was developed in-house and submitted upstream. The upstream bug

is:

http://bugs.proftpd.org/show_bug.cgi?id=4157

diff --git a/modules/mod_core.c b/modules/mod_core.c

--- a/modules/mod_core.c

+++ b/modules/mod_core.c

@@ -40,6 +40,7 @@

 /* From src/main.c */

 extern unsigned long max_connects;

 extern unsigned int max_connect_interval;

+extern unsigned char tracing_enabled;

 /* From modules/mod_site.c */

 extern modret_t *site_dispatch(cmd_rec*);

@@ -1381,6 +1382,8 @@

   int per_session = FALSE;

   unsigned int idx = 1;

+  tracing_enabled = TRUE;

+

   if (cmd->argc-1 < 1)

     CONF_ERROR(cmd, "wrong number of parameters");

   CHECK_CONF(cmd, CONF_ROOT);

diff --git a/modules/mod_ls.c b/modules/mod_ls.c

--- a/modules/mod_ls.c

+++ b/modules/mod_ls.c

@@ -307,10 +307,12 @@

 static int sendline(int flags, char *fmt, ...) {

   va_list msg;

-  char buf[PR_TUNABLE_BUFFER_SIZE+1] = {'\0'};

+  char buf[PR_TUNABLE_BUFFER_SIZE+1];

   int res = 0;

   size_t buflen, listbuflen;

+  (void) memset(buf, '\0', sizeof(buf));

+

   if (listbuf == NULL) {

     listbufsz = pr_config_get_server_xfer_bufsz(PR_NETIO_IO_WR);

     listbuf = listbuf_ptr = pcalloc(session.pool, listbufsz);

diff --git a/src/fsio.c b/src/fsio.c

--- a/src/fsio.c

+++ b/src/fsio.c

@@ -556,10 +556,12 @@

 static int cache_stat(pr_fs_t *fs, const char *path, struct stat *sbuf,

     unsigned int op) {

   int res = -1;

-  char pathbuf[PR_TUNABLE_PATH_MAX + 1] = {'\0'};

+  char pathbuf[PR_TUNABLE_PATH_MAX + 1];

   int (*mystat)(pr_fs_t *, const char *, struct stat *) = NULL;

   size_t pathlen;

+  (void) memset(pathbuf, '\0', sizeof(pathbuf));

+

   /* Sanity checks */

   if (fs == NULL) {

     errno = EINVAL;

@@ -641,8 +643,8 @@

  * during the hit.

  */

 static pr_fs_t *lookup_dir_fs(const char *path, int op) {

-  char buf[PR_TUNABLE_PATH_MAX + 1] = {'\0'};

-  char tmp_path[PR_TUNABLE_PATH_MAX + 1] = {'\0'};

+  char buf[PR_TUNABLE_PATH_MAX + 1];

+  char tmp_path[PR_TUNABLE_PATH_MAX + 1];

   pr_fs_t *fs = NULL;

   int exact = FALSE;

   size_t tmp_pathlen = 0;

@@ -651,6 +653,9 @@

   pr_fs_match_t *fsm = NULL;

 #endif /* PR_FS_MATCH */

+  (void) memset(buf, '\0', sizeof(buf));

+  (void) memset(tmp_path, '\0', sizeof(tmp_path));

+

   sstrncpy(buf, path, sizeof(buf));

   /* Check if the given path is an absolute path.  Since there may be

diff --git a/src/trace.c b/src/trace.c

--- a/src/trace.c

+++ b/src/trace.c

@@ -32,6 +32,8 @@

 #ifdef PR_USE_TRACE

+unsigned char tracing_enabled = FALSE;

+

 static int trace_logfd = -1;

 static unsigned long trace_opts = PR_TRACE_OPT_DEFAULT;

 static pool *trace_pool = NULL;

@@ -473,6 +475,10 @@

   int res;

   va_list msg;

+  /* Optimization: do not run tracing code unless explicitly enabled. */

+  if (tracing_enabled == FALSE)

+    return 0;

+

   va_start(msg, fmt);

   res = pr_trace_vmsg(channel, level, fmt, msg);

   va_end(msg);