signal: make do_sigpending() void

do_sigpending() returned 0 unconditionally so it doesn't make sense to
have it return at all.  This allows us to simplify a bunch of syscall
callers.

Link: http://lkml.kernel.org/r/20180602103653.18181-5-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -2753,7 +2753,7 @@ COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
 }
 #endif
 
-static int do_sigpending(sigset_t *set)
+static void do_sigpending(sigset_t *set)
 {
 	spin_lock_irq(&current->sighand->siglock);
 	sigorsets(set, &current->pending.signal,
@@ -2762,7 +2762,6 @@ static int do_sigpending(sigset_t *set)
 
 	/* Outside the lock because only this thread touches it.  */
 	sigandsets(set, &current->blocked, set);
-	return 0;
 }
 
 /**
@@ -2774,15 +2773,16 @@ static int do_sigpending(sigset_t *set)
 SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, uset, size_t, sigsetsize)
 {
 	sigset_t set;
-	int err;
 
 	if (sigsetsize > sizeof(*uset))
 		return -EINVAL;
 
-	err = do_sigpending(&set);
-	if (!err && copy_to_user(uset, &set, sigsetsize))
-		err = -EFAULT;
-	return err;
+	do_sigpending(&set);
+
+	if (copy_to_user(uset, &set, sigsetsize))
+		return -EFAULT;
+
+	return 0;
 }
 
 #ifdef CONFIG_COMPAT
@@ -2790,15 +2790,13 @@ COMPAT_SYSCALL_DEFINE2(rt_sigpending, compat_sigset_t __user *, uset,
 		compat_size_t, sigsetsize)
 {
 	sigset_t set;
-	int err;
 
 	if (sigsetsize > sizeof(*uset))
 		return -EINVAL;
 
-	err = do_sigpending(&set);
-	if (!err)
-		err = put_compat_sigset(uset, &set, sigsetsize);
-	return err;
+	do_sigpending(&set);
+
+	return put_compat_sigset(uset, &set, sigsetsize);
 }
 #endif
 
@@ -3560,25 +3558,26 @@ int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
 SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, uset)
 {
 	sigset_t set;
-	int err;
 
 	if (sizeof(old_sigset_t) > sizeof(*uset))
 		return -EINVAL;
 
-	err = do_sigpending(&set);
-	if (!err && copy_to_user(uset, &set, sizeof(old_sigset_t)))
-		err = -EFAULT;
-	return err;
+	do_sigpending(&set);
+
+	if (copy_to_user(uset, &set, sizeof(old_sigset_t)))
+		return -EFAULT;
+
+	return 0;
 }
 
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE1(sigpending, compat_old_sigset_t __user *, set32)
 {
 	sigset_t set;
-	int err = do_sigpending(&set);
-	if (!err)
-		err = put_user(set.sig[0], set32);
-	return err;
+
+	do_sigpending(&set);
+
+	return put_user(set.sig[0], set32);
 }
 #endif