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Date:   Tue, 1 Dec 2020 14:57:51 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     luto@kernel.org, tglx@linutronix.de, gofmanp@gmail.com,
        christian.brauner@ubuntu.com, peterz@infradead.org,
        willy@infradead.org, shuah@kernel.org,
        linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        linux-kselftest@vger.kernel.org, x86@kernel.org,
        kernel@collabora.com
Subject: Re: [PATCH v8 4/7] entry: Support Syscall User Dispatch on common
 syscall entry
Message-ID: <202012011457.047EFC2@keescook>
References: <20201127193238.821364-1-krisman@collabora.com>
 <20201127193238.821364-5-krisman@collabora.com>
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On Fri, Nov 27, 2020 at 02:32:35PM -0500, Gabriel Krisman Bertazi wrote:
> Syscall User Dispatch (SUD) must take precedence over seccomp and
> ptrace, since the use case is emulation (it can be invoked with a
> different ABI) such that seccomp filtering by syscall number doesn't
> make sense in the first place.  In addition, either the syscall is
> dispatched back to userspace, in which case there is no resource for to
> trace, or the syscall will be executed, and seccomp/ptrace will execute
> next.
> 
> Since SUD runs before tracepoints, it needs to be a SYSCALL_WORK_EXIT as
> well, just to prevent a trace exit event when dispatch was triggered.
> For that, the on_syscall_dispatch() examines context to skip the
> tracepoint, audit and other work.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

Acked-by: Kees Cook <keescook@chromium.org>


-- 
Kees Cook