linux-kernel - Re: [PATCH v8 4/7] entry: Support Syscall User Dispatch on common syscall entry

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Message-ID: <202012011457.047EFC2@keescook>
Date:   Tue, 1 Dec 2020 14:57:51 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     luto@...nel.org, tglx@...utronix.de, gofmanp@...il.com,
        christian.brauner@...ntu.com, peterz@...radead.org,
        willy@...radead.org, shuah@...nel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-kselftest@...r.kernel.org, x86@...nel.org,
        kernel@...labora.com
Subject: Re: [PATCH v8 4/7] entry: Support Syscall User Dispatch on common
 syscall entry

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@...labora.com>

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


-- 
Kees Cook