index 8944ce5..e7568ff 100644
@@ -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);

fs/fcntl.c +3 -4

index 549daf8..32c8677 100644
@@ -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);

include/linux/signal.h +2 -2

index 84f997f..cddf220 100644
@@ -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);

kernel/exit.c +2 -2

index 2d8be7e..096beb5 100644
@@ -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);

kernel/ptrace.c +1 -1

index 4c8bcd7..e8eb715 100644
@@ -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)

kernel/signal.c +2 -2

index 4530fc6..8355426 100644
@@ -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];

kernel/sys.c +1 -1

index 31deba8..06dc092 100644
@@ -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;
 			}

Américo Wang

author

2008-12-26 06:50 UTC #2 lore raw

Quoted 5 lines · Oleg Nesterov

Quoted 2 lines · Américo Wang
Teach valid_signal() to check sig > 0 case.
Why?

Just to simplify the checking.

Quoted 10 lines

drivers/char/vt_ioctl.c int vt_ioctl(struct tty_struct *tty, struct file * file, · line 730
Quoted 7 lines
drivers/char/vt_ioctl.c +1 -1
@@ -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)
                                 ^^^^^
The patch adds a lot of unnecessary typecasts like this.

because it's inline?

Quoted 10 lines

Quoted 7 lines

include/linux/signal.h +2 -2

-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;

}

This looks a bit strange, why not

Quoted 3 lines

	return sig > 0 && sig <= _NSIG;

Yes, this one is better.

Quoted 7 lines

But, more importantly, I don't think the patch is correct.
Unless I misread the patch, now kill(pid, 0) returns -EINVAL, no?
And we have other users of valid_signal() which assume that sig == 0 is OK, for example arch_ptrace().

Oh, thanks for pointing this out. I didn't know this. Sorry.

Quoted 8 lines

Imho, the patch has a point, but perhaps it is better to add the new helper and then convert the users which do something like
	if (valid_signal(sig) && sig)
		...
What do you think?

I think this is a good idea. I will do it.

Thanks.

Signature · 1 line

"Against stupidity, the gods themselves, contend in vain."

Ingo Molnar

2008-12-26 08:57 UTC #3 lore raw

Quoted 11 lines · Américo Wang

Quoted 9 lines
drivers/char/vt_ioctl.c int vt_ioctl(struct tty_struct *tty, struct file * file, · line 730
Quoted 6 lines
drivers/char/vt_ioctl.c +1 -1
@@ -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)
                                 ^^^^^
The patch adds a lot of unnecessary typecasts like this.
because it's inline?

Why does your patch add a lot of seemingly unnecessary typecasts? [if your short reply was supposed to be an answer to that question then please explain it in more detail.]

Ingo

Américo Wang

author

2008-12-26 09:17 UTC #4 lore raw

Quoted 11 lines · Ingo Molnar

Quoted 8 lines · Américo Wang

Quoted 8 lines

drivers/char/vt_ioctl.c int vt_ioctl(struct tty_struct *tty, struct file * file, · line 730

Quoted 6 lines

drivers/char/vt_ioctl.c +1 -1

@@ -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)

                                 ^^^^^

Quoted 7 lines

Quoted 3 lines
Quoted 1 line
The patch adds a lot of unnecessary typecasts like this.
because it's inline?
Why does your patch add a lot of seemingly unnecessary typecasts? [if your short reply was supposed to be an answer to that question then please explain it in more detail.]

Hi, Ingo.

because I also changed the type of valid_signal():

-static inline int valid_signal(unsigned long sig) +static inline int valid_signal(int sig)

I noticed that gcc put this kind of warning into -Wtraditional-conversion recently, but it is still useful to use explicit cast, isn't it?

Thanks.

Signature · 1 line

"Against stupidity, the gods themselves, contend in vain."

Oleg Nesterov

maintainer

2008-12-26 16:08 UTC #5 lore raw

Quoted 21 lines · Américo Wang

Quoted 11 lines · Ingo Molnar
Quoted 8 lines · Américo Wang
Quoted 8 lines
drivers/char/vt_ioctl.c int vt_ioctl(struct tty_struct *tty, struct file * file, · line 730
Quoted 6 lines
drivers/char/vt_ioctl.c +1 -1
@@ -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)
                                 ^^^^^
Quoted 7 lines
Quoted 3 lines
Quoted 1 line
The patch adds a lot of unnecessary typecasts like this.
because it's inline?
Why does your patch add a lot of seemingly unnecessary typecasts? [if your short reply was supposed to be an answer to that question then please explain it in more detail.]

Quoted 6 lines

Hi, Ingo.
because I also changed the type of valid_signal():
-static inline int valid_signal(unsigned long sig) +static inline int valid_signal(int sig)

and please note that this change itself is a bit dangerous. Suppose that a bad user does sys_prctl(PR_SET_PDEATHSIG, LONG_MIN | SIGCHLD), and now valid_signal(arg2) (or valid_signal((int)arg2)) returns T.

(nothing really bad happens because ->pdeath_signal is "int", but still).

Note also that it is correct to do prctl(PR_SET_PDEATHSIG, 0), so the patch was doubly wrong here.

So, please check very carefully every change you are going to do. Make sure you don't change the behaviour, unless you think the current code is buggy. In that case please document the fix.

OTOH, I don't understand why sys_mq_notify() accepts sigev_signo == 0, perhaps this is oversight. good_sigevent() looks correct, but should use the helper.

Quoted 3 lines

I noticed that gcc put this kind of warning into -Wtraditional-conversion recently, but it is still useful to use explicit cast, isn't it?

I'd say explicit casts should be avoided as much as possible.

As for this particular case. Note that valid_signa((int)long_arg) only helps to hide the problem.

Oleg.