netdev - Re: [PATCH v10 07/11] signal, x86: add SIGSYS info and make it synchronous.

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Date:	Thu, 23 Feb 2012 23:15:51 +0100
From:	"Indan Zupancic" <indan@....nu>
To:	"Will Drewry" <wad@...omium.org>
Cc:	"Roland McGrath" <mcgrathr@...gle.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Kees Cook" <keescook@...omium.org>,
	"Andrew Lutomirski" <luto@....edu>, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
	kernel-hardening@...ts.openwall.com, netdev@...r.kernel.org,
	x86@...nel.org, arnd@...db.de, davem@...emloft.net,
	mingo@...hat.com, oleg@...hat.com, peterz@...radead.org,
	rdunlap@...otime.net, tglx@...utronix.de, eparis@...hat.com,
	serge.hallyn@...onical.com, djm@...drot.org, scarybeasts@...il.com,
	pmoore@...hat.com, akpm@...ux-foundation.org, corbet@....net,
	eric.dumazet@...il.com, markus@...omium.org
Subject: Re: [PATCH v10 07/11] signal, x86: add SIGSYS info and make it
 synchronous.

On Thu, February 23, 2012 20:26, Will Drewry wrote:
> Seems like there's an argument for another return code,
> SECCOMP_RET_CORE, that resets/unblocks the SIGSYS handler since the
> existing TRAP and KILL options seem to cover the other paths (signal
> handler and do_exit).

What about making SECCOMP_RET_TRAP dump core/send SIGSYS if there is
no tracer with PTRACE_O_SECCOMP set? And perhaps go for a blockable
SIGSYS? That way you only have KILL, ERRNO and TRAP, with the last
one meaning deny, but giving someone else a chance to do something.
Or is that just confusing?

I don't think there should be too many return values, or else you
put too much runtime policy into the filters.

Sending SIGSYS is useful, but it's quite a bit less useful if user
space can't handle it in a signal handler, so I don't think it's
worth it to make a unblockable version.

Greetings,

Indan

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