Fix mailbox corruption in imap4d.

Delivery of a signal when a previous signal was being handled caused
mailbox corruption.

* imap4d/imap4d.c (imap4d_child_signal_setup): New function.
(imap4d_mainloop): Call imap4d_child_signal_setup.
* imap4d/signal.c (imap4d_child_signal): Reset all signal handlers
before doing actual job.
* lib/signal.c (mu_set_signals): Use sigaction.

@@ -383,18 +383,22 @@ get_client_address (int fd, struct sockaddr_in *pcs)
   return 0;
 }
 
+void
+imap4d_child_signal_setup (RETSIGTYPE (*handler) (int signo))
+{
+  static int sigtab[] = { SIGILL, SIGBUS, SIGFPE, SIGSEGV, SIGSTOP, SIGPIPE,
+			  SIGABRT, SIGINT, SIGQUIT, SIGTERM, SIGHUP, SIGALRM };
+  mu_set_signals (handler, sigtab, MU_ARRAY_SIZE (sigtab));
+}
+
 static int
 imap4d_mainloop (int fd, FILE *infile, FILE *outfile)
 {
   imap4d_tokbuf_t tokp;
   char *text;
   int debug_mode = isatty (fd);
-  static int sigtab[] = { SIGILL, SIGBUS, SIGFPE, SIGSEGV, SIGSTOP, SIGPIPE,
-			  SIGABRT, SIGINT, SIGQUIT, SIGTERM, SIGHUP, SIGALRM };
 
-  /* Reset signals */
-  mu_set_signals (imap4d_child_signal, sigtab, MU_ARRAY_SIZE (sigtab));
-  
+  imap4d_child_signal_setup (imap4d_child_signal);
   util_setio (infile, outfile);
 
   if (imap4d_preauth_setup (fd) == 0)

@@ -49,21 +49,25 @@ imap4d_master_signal (int signo)
 RETSIGTYPE
 imap4d_child_signal (int signo)
 {
+  imap4d_child_signal_setup (SIG_IGN);
   mu_diag_output (MU_DIAG_CRIT, _("got signal `%s'"), strsignal (signo));
-
   switch (signo)
     {
     case SIGTERM:
     case SIGHUP:
-      imap4d_bye (ERR_TERMINATE);
-
+      signo = ERR_TERMINATE;
+      break;
+      
     case SIGALRM:
-      imap4d_bye (ERR_TIMEOUT);
-
+      signo = ERR_TIMEOUT;
+      break;
+      
     case SIGPIPE:
-      imap4d_bye (ERR_NO_OFILE);
+      signo = ERR_NO_OFILE;
+      break;
       
     default:
-      imap4d_bye (ERR_SIGNAL);
+      signo = ERR_SIGNAL;
     }
+  imap4d_bye (signo);
 }

@@ -26,7 +26,16 @@ void
 mu_set_signals (RETSIGTYPE (*handler) (int signo), int *sigv, int sigc)
 {
   int i;
+  struct sigaction act;
 
+  act.sa_flags = 0;
+  sigemptyset (&act.sa_mask);
   for (i = 0; i < sigc; i++)
-    signal (sigv[i], handler);
+    sigaddset (&act.sa_mask, i);
+      
+  for (i = 0; i < sigc; i++)
+    {
+      act.sa_handler = handler;
+      sigaction (sigv[i], &act, NULL);
+    }
 }