stty: ensure arbitrary data is not displayed

* src/stty.c (main): Use static structures to ensure
they're initialized (to zero), so that random data is
not displayed, or compared resulting in a inaccurate
failure reported to users.  This was seen on musl libc
where some parts of the termios c_cc array were
not initialized by tcgetattr().
Reported by Bruno Haible.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/stty.c b/src/stty.c
index fb7feefab..607a4e7bb 100644
--- a/src/stty.c
+++ b/src/stty.c
@@ -1290,7 +1290,9 @@ apply_settings (bool checking, char const *device_name,
 int
 main (int argc, char **argv)
 {
-  struct termios mode;
+  /* Initialize to all zeroes so there is no risk memcmp will report a
+     spurious difference in an uninitialized portion of the structure.  */
+  static struct termios mode;
 
   enum output_type output_type;
   int optc;
@@ -1426,7 +1428,9 @@ main (int argc, char **argv)
 
   if (require_set_attr)
     {
-      struct termios new_mode;
+      /* Initialize to all zeroes so there is no risk memcmp will report a
+         spurious difference in an uninitialized portion of the structure.  */
+      static struct termios new_mode;
 
       if (tcsetattr (STDIN_FILENO, tcsetattr_options, &mode))
         die (EXIT_FAILURE, errno, "%s", quotef (device_name));