From: Rich Felker <dalias@libc.org>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: Carlos O'Donell via Libc-alpha <libc-alpha@sourceware.org>
Subject: Re: [PATCH] Make abort() AS-safe (Bug 26275).
Date: Tue, 29 Sep 2020 10:42:07 -0400 [thread overview]
Message-ID: <20200929144207.GD17637@brightrain.aerifal.cx> (raw)
In-Reply-To: <87d025jcn0.fsf@mid.deneb.enyo.de>
On Tue, Sep 29, 2020 at 08:54:59AM +0200, Florian Weimer wrote:
> * Rich Felker:
>
> > Is there a reason to take the lock across fork rather than just
> > resetting it in the child? After seeing this I'm working on fixing the
> > same issue in musl and was about to take the lock, but realized ours
> > isn't actually protecting any userspace data state, just excluding
> > sigaction on SIGABRT during abort.
>
> It's also necessary to stop the fork because the subprocess could
> otherwise observe the impossible SIG_DFL state. In case the signal
> handler returns, the implementation needs to produce a termination
> status with SIGABRT as the termination signal, and the only way I can
> see to achieve that is to remove the signal handler and send the
> signal again. This suggests that a lock in sigaction is needed as
> well.
Yes, in musl we already have the lock in sigaction -- that's the whole
point of the lock. To prevent other threads from fighting to change
the disposition back to SIG_IGN or a signal handler while abort is
trying to change it to SIG_DFL.
> But for the fork case, restting the lock in the new subprocess should
> be sufficient.
I don't follow. Do you mean taking the lock in the parent, but just
resetting it in the child? That should work but I don't see how it has
any advantage over just releasing it in the child.
Rich
next prev parent reply other threads:[~2020-09-29 14:42 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-27 14:19 Carlos O'Donell
2020-09-27 20:04 ` Florian Weimer
2020-09-28 23:48 ` Rich Felker
2020-09-29 6:54 ` Florian Weimer
2020-09-29 14:42 ` Rich Felker [this message]
2020-10-01 2:30 ` Rich Felker
2020-10-01 6:08 ` Florian Weimer
2020-10-01 14:39 ` [musl] " Rich Felker
2020-10-01 15:11 ` Florian Weimer
2020-10-01 15:28 ` Rich Felker
2020-10-01 14:49 ` Carlos O'Donell
2020-10-01 14:55 ` [musl] " Rich Felker
2020-10-10 0:26 ` Rich Felker
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