Add support for forcing default signal handlers to flush_signal_handlers().

Make kmod force default handlers before executing the user process.

fs/exec.c

@@ -821,7 +821,7 @@ int flush_old_exec(struct linux_binprm * bprm)
 	   
 	current->self_exec_id++;
 			
-	flush_signal_handlers(current);
+	flush_signal_handlers(current, 0);
 	flush_old_files(current->files);
 	exit_itimers(current);
 

include/linux/sched.h

@@ -534,7 +534,7 @@ extern int in_egroup_p(gid_t);
 
 extern void proc_caches_init(void);
 extern void flush_signals(struct task_struct *);
-extern void flush_signal_handlers(struct task_struct *);
+extern void flush_signal_handlers(struct task_struct *, int force_default);
 extern int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info);
 extern void block_all_signals(int (*notifier)(void *priv), void *priv,
 			      sigset_t *mask);

kernel/kmod.c

@@ -155,7 +155,7 @@ static int ____call_usermodehelper(void *data)
 	/* Unblock all signals. */
 	flush_signals(current);
 	spin_lock_irq(&current->sighand->siglock);
-	flush_signal_handlers(current);
+	flush_signal_handlers(current, 1);
 	sigemptyset(&current->blocked);
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);

kernel/signal.c

@@ -356,12 +356,12 @@ void exit_signal(struct task_struct *tsk)
  */
 
 void
-flush_signal_handlers(struct task_struct *t)
+flush_signal_handlers(struct task_struct *t, int force_default)
 {
 	int i;
 	struct k_sigaction *ka = &t->sighand->action[0];
 	for (i = _NSIG ; i != 0 ; i--) {
-		if (ka->sa.sa_handler != SIG_IGN)
+		if (force_default || ka->sa.sa_handler != SIG_IGN)
 			ka->sa.sa_handler = SIG_DFL;
 		ka->sa.sa_flags = 0;
 		sigemptyset(&ka->sa.sa_mask);