signals: consolidate checks for whether or not to ignore a signal

Both sig_ignored() and do_sigaction() check for signr to be explicitly or
implicitly ignored.  Introduce a helper for them.

This patch is aimed to help handling signals by pid namespace's init, and was
derived from one of Oleg's patches
https://lists.linux-foundation.org/pipermail/containers/2007-December/009308.html
so, if he doesn't mind, he should be considered as an author.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 10 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 4a45bac2c632..24ee53b7f60c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -39,11 +39,19 @@
 
 static struct kmem_cache *sigqueue_cachep;
 
+static int __sig_ignored(struct task_struct *t, int sig)
+{
+        void __user *handler;
+
+        /* Is it explicitly or implicitly ignored? */
+
+        handler = t->sighand->action[sig - 1].sa.sa_handler;
+        return handler == SIG_IGN ||
+                (handler == SIG_DFL && sig_kernel_ignore(sig));
+}
 
 static int sig_ignored(struct task_struct *t, int sig)
 {
-        void __user * handler;
-
         /*
          * Tracers always want to know about signals..
          */
@@ -58,10 +66,7 @@ static int sig_ignored(struct task_struct *t, int sig)
         if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
                 return 0;
 
-        /* Is it explicitly or implicitly ignored? */
-        handler = t->sighand->action[sig-1].sa.sa_handler;
-        return   handler == SIG_IGN ||
-                (handler == SIG_DFL && sig_kernel_ignore(sig));
+        return __sig_ignored(t, sig);
 }
 
 /*
@@ -2331,13 +2336,14 @@ sys_rt_sigqueueinfo(int pid, int sig, siginfo_t __user *uinfo)
 
 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 {
+        struct task_struct *t = current;
         struct k_sigaction *k;
         sigset_t mask;
 
         if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
                 return -EINVAL;
 
-        k = &current->sighand->action[sig-1];
+        k = &t->sighand->action[sig-1];
 
         spin_lock_irq(&current->sighand->siglock);
         if (oact)
@@ -2358,9 +2364,7 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
                  *   (for example, SIGCHLD), shall cause the pending signal to
                  *   be discarded, whether or not it is blocked"
                  */
-                if (act->sa.sa_handler == SIG_IGN ||
-                   (act->sa.sa_handler == SIG_DFL && sig_kernel_ignore(sig))) {
-                        struct task_struct *t = current;
+                if (__sig_ignored(t, sig)) {
                         sigemptyset(&mask);
                         sigaddset(&mask, sig);
                         rm_from_queue_full(&mask, &t->signal->shared_pending);