Re: [Regression v4.2 ?] 32-bit seccomp-BPF returned errno values wrong in VM?

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@chromium.org>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	David Drysdale <drysdale@google.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Will Drewry <wad@chromium.org>, Ingo Molnar <mingo@kernel.org>,
	Alok Kataria <akataria@vmware.com>,
	Borislav Petkov <bp@alien8.de>,
	Alexei Starovoitov <ast@plumgrid.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>, X86 ML <x86@kernel.org>
Subject: Re: [Regression v4.2 ?] 32-bit seccomp-BPF returned errno values wrong in VM?
Date: Thu, 13 Aug 2015 16:30:19 -0700	[thread overview]
Message-ID: <CA+55aFykr1_3VmtKDvRCkcKq0y=y0vPMxeZzcBmQrQYuAN2r1w@mail.gmail.com> (raw)
In-Reply-To: <CALCETrXGJQ33hDJ-GcVfrYx2qh0ewBwU5=o70UE=XuP+H2hz3g@mail.gmail.com>

On Thu, Aug 13, 2015 at 3:59 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>
> Kees, would it be straightforward to rig up the seccomp tests to
> automatically test compat?  The x86 selftests automatically test both
> native and compat, and that might be usable as a model.  I did that
> because it's extremely easy to regress one and not the other.

Note that in this case, the bug was actually _hidden_ by audit (since
the audit path would end up reloading %rax, and is why doing "auditctl
-a task,never" actually enabled people to see it), so it would also be
good to try to make sure that the tests would try both with and
without audit involved too.

I'm very tired of these bugs, but I guess and hope that your patches
to move as much as possible of this to C will actually end up helping
in the long run. So while I'm not really looking forward to even
_more_ patches to the low-level asm, at least the C rewrite seems more
worthwhile than some of the noise that made this all so painful has
felt.

                 Linus