Re: SIGFPE handler is naive

Noah Misch <noah(at)leadboat(dot)com> writes:
> On Tue, Aug 14, 2012 at 08:40:06AM -0400, Robert Haas wrote:
>> On Tue, Aug 14, 2012 at 6:50 AM, Greg Stark <stark(at)mit(dot)edu> wrote:
>>> It is possible to check if the signal was synchronous or was sent from
>>> an external process. You can check siginfo->si_pid to see who sent you
>>> the signal. I'm not sure checking that and handling it at
>>> check_for_interrupts if it's asynchronous is the best solution or not
>>> though.

>> If that's portable it might be an option, but I doubt that it is.

> I suspect it is portable.

Single Unix Spec V2 says (on the sigaction man page)

The si_code member contains a code identifying the cause of the
signal. If the value of si_code is less than or equal to 0, then the
signal was generated by a process and si_pid and si_uid respectively
indicate the process ID and the real user ID of the sender.

I'm not sure I would trust checking si_pid alone; it would definitely
fail on my old HPUX box, where I see that field is union'ed with si_addr
and so will read as garbage for a locally-sourced SIGFPE. But it might
be that checking si_code alone would work reliably.

I think that rejecting an externally sourced SIGFPE might be worth doing
if we can distinguish that reliably.

regards, tom lane