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raise(-1) succeeds for programs linked against libpthread

From: Ludovic Courtès
Subject: raise(-1) succeeds for programs linked against libpthread
Date: Tue, 13 Oct 2020 15:41:37 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)


(Cc: bug-hurd.)

Jan Nieuwenhuizen <janneke@gnu.org> skribis:

>>> #include <signal.h>
>>> int
>>> main (void)
>>> {
>>>   if (!raise (-1))
>>>     return 1;
>>>   return 0;
>>> }
>> I don’t know if it’s relevant here, but you should always use ‘-pthread’
>> both at compile time and link time:
>>   gcc raise.c -pthread
>> That typically defines a few macros that may or may not have an effect
>> on the code at hand.
> Ah...right.  Makes no difference, though:
> root@childhurd ~# guix environment --bootstrap --ad-hoc gcc-toolchain@7
> root@childhurd ~ [env]# gcc raise.c
> root@childhurd ~ [env]# ./a.out
> root@childhurd ~ [env]# echo $?
> 0
> root@childhurd ~ [env]# gcc raise.c -pthread
> root@childhurd ~ [env]# ./a.out
> User defined signal 2

Interesting!  In the second case, we’re using ‘__pthread_kill’ from
‘pt-kill.c’ (instead of ‘kill’).

The expected behavior is that ‘raise’ should return non-zero and EINVAL.

‘pthread_kill’ passes the signal number to ‘_hurd_raise_signal’, which
assumes it is valid:

--8<---------------cut here---------------start------------->8---
_hurd_raise_signal (struct hurd_sigstate *ss,
                    int signo, const struct hurd_signal_detail *detail)
  if (ss == NULL)
      ss = _hurd_self_sigstate ();
      __spin_lock (&ss->lock);

  /* Mark SIGNO as pending to be delivered.  */
  __sigaddset (&ss->pending, signo);
  ss->pending_data[signo] = *detail;
--8<---------------cut here---------------end--------------->8---

I suppose that before calling ‘sigaddset’, it should check whether SIGNO
is within bounds, along the lines of:

  if (signo < 2 || signo >= _NSIG)
    return EINVAL;

Does that make sense?


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