Re: [PATCH v2] exec: don't force_sigsegv processes with a pending fatal signal

Ivan Delalande
2019-02-11T23:20:45Z

On Mon, Feb 11, 2019 at 06:12:53PM +0100, Oleg Nesterov wrote:
> sorry, I couldn't look at this patch before.
>
> On 02/04, Ivan Delalande wrote:
> >
> > --- a/fs/exec.c
> > +++ b/fs/exec.c
> > @@ -1660,7 +1660,12 @@ int search_binary_handler(struct linux_binprm *bprm)
> > if (retval < 0 && !bprm->mm) {
> > /* we got to flush_old_exec() and failed after it */
> > read_unlock(&binfmt_lock);
> > - force_sigsegv(SIGSEGV, current);
> > + if (!fatal_signal_pending(current)) {
> > + if (print_fatal_signals)
> > + pr_info("load_binary() failed: %d\n",
> > + retval);
>
> I won't argue, but do we really want this spam?
>
> > + force_sigsegv(SIGSEGV, current);
> > + }
> > return retval;
> > }
> > if (retval != -ENOEXEC || !bprm->file) {
> > diff --git a/kernel/signal.c b/kernel/signal.c
> > index e1d7ad8e6ab1..674076e63624 100644
> > --- a/kernel/signal.c
> > +++ b/kernel/signal.c
> > @@ -2552,10 +2552,10 @@ static void signal_delivered(struct ksignal *ksig, int stepping)
> >
> > void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
> > {
> > - if (failed)
> > - force_sigsegv(ksig->sig, current);
> > - else
> > + if (!failed)
> > signal_delivered(ksig, stepping);
> > + else if (!fatal_signal_pending(current))
> > + force_sigsegv(ksig->sig, current);
>
> The changelog doesn't explain this change.
>
> OK, I guess it comes from the previous discussion, setup_rt_frame() can equally fail
> if fatal_signal_pending(). But this should be documented at least in the changelog,
> and I still think we could simply change force_sigsegv() instead.
>
> In any case, Eric has already mentioned that we going to give SIGKILL more priority,
> so I think we can drop this patch?

Yes, I've been running our tests on top of Eric's tree over the week-end
and haven't seen any new hit. I also see that Andrew has dropped the
patch from -mm, so no futher action should be required here.

Thank you for taking a look at the patch anyway.

--
Ivan Delalande
Arista Networks