2 files changed, 25 insertions, 5 deletions

diff --git a/include/linux/signal.h b/include/linux/signal.h
index fcd2b14b1932..ba009c167275 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -243,6 +243,7 @@ extern long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig,
                                  siginfo_t *info);
 extern long do_sigpending(void __user *, unsigned long);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
+extern void set_current_blocked(const sigset_t *);
 extern int show_unhandled_signals;
 
 struct pt_regs;
diff --git a/kernel/signal.c b/kernel/signal.c
index e8308e3238c1..8aa3a2e226af 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2299,6 +2299,29 @@ long do_no_restart_syscall(struct restart_block *param)
         return -EINTR;
 }
 
+/**
+ * set_current_blocked - change current->blocked mask
+ * @newset: new mask
+ *
+ * It is wrong to change ->blocked directly, this helper should be used
+ * to ensure the process can't miss a shared signal we are going to block.
+ */
+void set_current_blocked(const sigset_t *newset)
+{
+        struct task_struct *tsk = current;
+
+        spin_lock_irq(&tsk->sighand->siglock);
+        if (signal_pending(tsk) && !thread_group_empty(tsk)) {
+                sigset_t newblocked;
+                /* A set of now blocked but previously unblocked signals. */
+                signandsets(&newblocked, newset, &current->blocked);
+                retarget_shared_pending(tsk, &newblocked);
+        }
+        tsk->blocked = *newset;
+        recalc_sigpending();
+        spin_unlock_irq(&tsk->sighand->siglock);
+}
+
 /*
  * This is also useful for kernel threads that want to temporarily
  * (or permanently) block certain signals.
@@ -2330,11 +2353,7 @@ int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
                 return -EINVAL;
         }
 
-        spin_lock_irq(&tsk->sighand->siglock);
-        tsk->blocked = newset;
-        recalc_sigpending();
-        spin_unlock_irq(&tsk->sighand->siglock);
-
+        set_current_blocked(&newset);
         return 0;
 }