[PATCH] sigaction should clear all signals on SIG_IGN, not just < 32

While rooting aroung in the signal code trying to understand how to fix the
SIG_IGN ploy (set sig handler to SIG_IGN and flood system with high speed
repeating timers) I came across what, I think, is a problem in sigaction()
in that when processing a SIG_IGN request it flushes signals from 1 to
SIGRTMIN and leaves the rest.  Attempt to fix this.

Signed-off-by: George Anzinger <george@mvista.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 49 insertions, 2 deletions

diff --git a/include/linux/signal.h b/include/linux/signal.h
index ea9eff16c4b7..b7d093520bb6 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -94,6 +94,23 @@ static inline int sigfindinword(unsigned long word)
 
 #endif /* __HAVE_ARCH_SIG_BITOPS */
 
+static inline int sigisemptyset(sigset_t *set)
+{
+        extern void _NSIG_WORDS_is_unsupported_size(void);
+        switch (_NSIG_WORDS) {
+        case 4:
+                return (set->sig[3] | set->sig[2] |
+                        set->sig[1] | set->sig[0]) == 0;
+        case 2:
+                return (set->sig[1] | set->sig[0]) == 0;
+        case 1:
+                return set->sig[0] == 0;
+        default:
+                _NSIG_WORDS_is_unsupported_size();
+                return 0;
+        }
+}
+
 #define sigmask(sig)    (1UL << ((sig) - 1))
 
 #ifndef __HAVE_ARCH_SIG_SETOPS
diff --git a/kernel/signal.c b/kernel/signal.c
index 9b6fda5e87f1..e20724af9b36 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -625,6 +625,33 @@ void signal_wake_up(struct task_struct *t, int resume)
  * Returns 1 if any signals were found.
  *
  * All callers must be holding the siglock.
+ *
+ * This version takes a sigset mask and looks at all signals,
+ * not just those in the first mask word.
+ */
+static int rm_from_queue_full(sigset_t *mask, struct sigpending *s)
+{
+        struct sigqueue *q, *n;
+        sigset_t m;
+
+        sigandsets(&m, mask, &s->signal);
+        if (sigisemptyset(&m))
+                return 0;
+
+        signandsets(&s->signal, &s->signal, mask);
+        list_for_each_entry_safe(q, n, &s->list, list) {
+                if (sigismember(mask, q->info.si_signo)) {
+                        list_del_init(&q->list);
+                        __sigqueue_free(q);
+                }
+        }
+        return 1;
+}
+/*
+ * Remove signals in mask from the pending set and queue.
+ * Returns 1 if any signals were found.
+ *
+ * All callers must be holding the siglock.
  */
 static int rm_from_queue(unsigned long mask, struct sigpending *s)
 {
@@ -2408,6 +2435,7 @@ int
 do_sigaction(int sig, const struct k_sigaction *act, struct k_sigaction *oact)
 {
         struct k_sigaction *k;
+        sigset_t mask;
 
         if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
                 return -EINVAL;
@@ -2455,9 +2483,11 @@ do_sigaction(int sig, const struct k_sigaction *act, struct k_sigaction *oact)
                         *k = *act;
                         sigdelsetmask(&k->sa.sa_mask,
                                       sigmask(SIGKILL) | sigmask(SIGSTOP));
-                        rm_from_queue(sigmask(sig), &t->signal->shared_pending);
+                        sigemptyset(&mask);
+                        sigaddset(&mask, sig);
+                        rm_from_queue_full(&mask, &t->signal->shared_pending);
                         do {
-                                rm_from_queue(sigmask(sig), &t->pending);
+                                rm_from_queue_full(&mask, &t->pending);
                                 recalc_sigpending_tsk(t);
                                 t = next_thread(t);
                         } while (t != current);