linux-kernel - Re: [PATCH 3/4] sh: Add SECCOMP

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Message-ID: <54a4db1a-1d41-7fa2-cb74-460256d3be0d@physik.fu-berlin.de>
Date:   Thu, 3 Sep 2020 08:03:06 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Rich Felker <dalias@...c.org>
Cc:     Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>,
        linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>
Subject: Re: [PATCH 3/4] sh: Add SECCOMP_FILTER

Hi Richi!

On 9/3/20 5:56 AM, Rich Felker wrote:
>> Test 51-live-user_notification%%001-00001 result:   FAILURE 51-live-user_notification 5 ALLOW rc=14
> 
> AFAICT, this test is buggy and cannot possibly work. It attempts to
> have SYS_getpid return a 64-bit value and check that the returned
> value matches. On 32-bit archs this will be truncated to 32 bits, but
> the comparison in the caller still compares against the full 64-bit
> value. I have no idea how this seemed to work before.

You're actually right, I forgot about that. Michael discovered this bug as well
and it was consequently fixed:

> https://github.com/seccomp/libseccomp/commit/bee43d3e884788569860a384e6a38357785a3995

>> Test 58-live-tsync_notify%%001-00001 result:   FAILURE 58-live-tsync_notify 6 ALLOW rc=14
> 
> This is similar to 51.
> 
> I think the commonality of all the failures is that they deal with
> return values set by seccomp filters for blocked syscalls, which are
> getting clobbered by ENOSYS from the failed syscall here. So I do need
> to keep the code path that jumps over the actual syscall if
> do_syscall_trace_enter returns -1, but that means
> do_syscall_trace_enter must now be responsible for setting the return
> value in non-seccomp failure paths.

Same here:

> https://github.com/seccomp/libseccomp/commit/f0686d9de911e7ffcdc7364566c1d146e44657c2

Not sure about the other two tests. I can re-base and re-test.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
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