[PING] [PATCH] pt_chown: Clear any signal mask inherited from the parent process.

[Geoffrey Thomas]

If grantpt() is called from a thread that is masking signals (for 
instance, from a program using signalfd or using a dedicated 
signal-handling thread), then that mask will get inherited to pt_chown. 
This means that signals like SIGINT will not interrup pt_chown, so if it 
hangs (e.g., because getgrnam("tty") hangs on a remote name service), 
Ctrl-C will terminate the parent process but leave pt_chown around. Since 
it's setuid, it's hard to kill any other way.

It is safe for pt_chown to unmask all signals, because grantpt() can be 
(and usually is) called from an unprivileged process with all signals 
unmasked.

---
  login/programs/pt_chown.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/login/programs/pt_chown.c b/login/programs/pt_chown.c
index e8d4716..ec78538 100644
--- a/login/programs/pt_chown.c
+++ b/login/programs/pt_chown.c
@@ -23,6 +23,7 @@
  #include <grp.h>
  #include <libintl.h>
  #include <locale.h>
+#include <signal.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
@@ -148,6 +149,11 @@ main (int argc, char *argv[])
    uid_t euid = geteuid ();
    uid_t uid = getuid ();
    int remaining;
+  sigset_t signalset;
+
+  /* Clear any signal mask from the parent process.  */
+  sigemptyset (&signalset);
+  sigprocmask (SIG_SETMASK, &signalset, NULL);

    if (argc == 1 && euid == 0)
      {
-- 
1.9.1