jobs: Always reset SIGINT/SIGQUIT handlers

jobs: Always reset SIGINT/SIGQUIT handlers

On Fri, Jan 08, 2021 at 08:55:41PM +0000, Harald van Dijk wrote:
> On 18/05/2018 19:39, Herbert Xu wrote:
> > This patch adds basic vfork support for the case of a simple command.
> > ...  @@ -879,17 +892,30 @@ forkchild(struct job *jp, union node *n, int
> > mode)
> >   		}
> >   	}
> >   	if (!oldlvl && iflag) {
> > -		setsignal(SIGINT);
> > -		setsignal(SIGQUIT);
> > +		if (mode != FORK_BG) {
> > +			setsignal(SIGINT);
> > +			setsignal(SIGQUIT);
> > +		}
> >   		setsignal(SIGTERM);
> >   	}
> > +
> > +	if (lvforked)
> > +		return;
> > +
> >   	for (jp = curjob; jp; jp = jp->prev_job)
> >   		freejob(jp);
> >   }
>
> This leaves SIGQUIT ignored in background jobs in interactive shells.
>
>   ENV= dash -ic 'dash -c "kill -QUIT \$\$; echo huh" & wait'
>
> As of dash 0.5.11, this prints "huh". Before, the subprocess process killed
> itself before it could print anything. Other shells do not leave SIGQUIT
> ignored.
>
> (In a few other shells, this also prints "huh", but in those other shells,
> that is because the inner shell chooses to ignore SIGQUIT, not because the
> outer shell leaves it ignored.)

Thanks for catching this.  I have no idea how that got in there
and it makes no sense whatsoever.  This patch removes the if
conditional.

Fixes: e94a964e7dd0 ("eval: Add vfork support")
Reported-by: Harald van Dijk <harald@gigawatt.nl>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>