[Patch] signal: let valid_signal() check more

["Américo Wang" <xiyou.wangcong@gmail.com>]

Teach valid_signal() to check sig > 0 case.

Tested on UML only.

Signed-off-by: WANG Cong <wangcong@zeuux.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>

---
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index 8944ce5..e7568ff 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -727,7 +727,7 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
 	{
 		if (!perm || !capable(CAP_KILL))
 			goto eperm;
-		if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
+		if (!valid_signal((int)arg) || arg == SIGKILL)
 			ret = -EINVAL;
 		else {
 			spin_lock_irq(&vt_spawn_con.lock);
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 549daf8..32c8677 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -313,11 +313,10 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 		break;
 	case F_SETSIG:
 		/* arg == 0 restores default behaviour. */
-		if (!valid_signal(arg)) {
-			break;
+		if (arg == 0 || valid_signal((int)arg)) {
+			err = 0;
+			filp->f_owner.signum = arg;
 		}
-		err = 0;
-		filp->f_owner.signum = arg;
 		break;
 	case F_GETLEASE:
 		err = fcntl_getlease(filp);
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 84f997f..cddf220 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -227,9 +227,9 @@ static inline void init_sigpending(struct sigpending *sig)
 extern void flush_sigqueue(struct sigpending *queue);
 
 /* Test if 'sig' is valid signal. Use this instead of testing _NSIG directly */
-static inline int valid_signal(unsigned long sig)
+static inline int valid_signal(int sig)
 {
-	return sig <= _NSIG ? 1 : 0;
+	return sig <= _NSIG ? (sig > 0) : 0;
 }
 
 extern int next_signal(struct sigpending *pending, sigset_t *mask);
diff --git a/kernel/exit.c b/kernel/exit.c
index 2d8be7e..096beb5 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -376,7 +376,7 @@ static void set_special_pids(struct pid *pid)
  */
 int allow_signal(int sig)
 {
-	if (!valid_signal(sig) || sig < 1)
+	if (!valid_signal(sig))
 		return -EINVAL;
 
 	spin_lock_irq(&current->sighand->siglock);
@@ -397,7 +397,7 @@ EXPORT_SYMBOL(allow_signal);
 
 int disallow_signal(int sig)
 {
-	if (!valid_signal(sig) || sig < 1)
+	if (!valid_signal(sig))
 		return -EINVAL;
 
 	spin_lock_irq(&current->sighand->siglock);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4c8bcd7..e8eb715 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -369,7 +369,7 @@ static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 
 static int ptrace_resume(struct task_struct *child, long request, long data)
 {
-	if (!valid_signal(data))
+	if (!valid_signal((int)data))
 		return -EIO;
 
 	if (request == PTRACE_SYSCALL)
diff --git a/kernel/signal.c b/kernel/signal.c
index 4530fc6..8355426 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1411,7 +1411,7 @@ int do_notify_parent(struct task_struct *tsk, int sig)
 		if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
 			sig = -1;
 	}
-	if (valid_signal(sig) && sig > 0)
+	if (valid_signal(sig))
 		__group_send_sig_info(sig, &info, tsk->parent);
 	__wake_up_parent(tsk, tsk->parent);
 	spin_unlock_irqrestore(&psig->siglock, flags);
@@ -2308,7 +2308,7 @@ int do_sigaction(int sig, 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)))
+	if (!valid_signal(sig) || (act && sig_kernel_only(sig)))
 		return -EINVAL;
 
 	k = &t->sighand->action[sig-1];
diff --git a/kernel/sys.c b/kernel/sys.c
index 31deba8..06dc092 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1631,7 +1631,7 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 
 	switch (option) {
 		case PR_SET_PDEATHSIG:
-			if (!valid_signal(arg2)) {
+			if (!valid_signal((int)arg2)) {
 				error = -EINVAL;
 				break;
 			}