linux-kernel - Re: [PATCH 13/15] selftests/seccomp: powerpc: Set syscall return during ptrace syscall exit

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Date:   Mon, 14 Sep 2020 13:20:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Christian Brauner <christian@...uner.io>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        linux-kselftest@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org,
        linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 13/15] selftests/seccomp: powerpc: Set syscall return
 during ptrace syscall exit

On Mon, Sep 14, 2020 at 03:47:13PM +1000, Michael Ellerman wrote:
> Kees Cook <keescook@...omium.org> writes:
> > Some archs (like ppc) only support changing the return code during
> > syscall exit when ptrace is used. As the syscall number might not
> > be available anymore during syscall exit, it needs to be saved
> > during syscall enter. Adjust the ptrace tests to do this.
> 
> I'm not that across all the fixture stuff, but if I'm reading it right
> you're now calling change_syscall() on both entry and exit for all
> arches.

Correct.

> That should work, but it no longer tests changing the return code on
> entry on the arches that support it, which seems like a backward step?

That's a good point. I wouldn't be in a position to notice a regression
for the other architectures. I will refactor this one...

-- 
Kees Cook