linux-kernel - Re: [PATCH v4 1/2] kernel: Implement selective syscall userspace redirection

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Message-ID: <202007161425.3D9B91DB6@keescook>
Date:   Thu, 16 Jul 2020 14:26:30 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Gabriel Krisman Bertazi <krisman@...labora.com>,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        kernel@...labora.com, luto@...nel.org, gofmanp@...il.com,
        linux-kselftest@...r.kernel.org, shuah@...nel.org
Subject: Re: [PATCH v4 1/2] kernel: Implement selective syscall userspace
 redirection

On Thu, Jul 16, 2020 at 10:06:01PM +0100, Matthew Wilcox wrote:
> On Thu, Jul 16, 2020 at 03:31:40PM -0400, Gabriel Krisman Bertazi wrote:
> > selector is an optional pointer to a char-sized userspace memory region
> > that has a key switch for the mechanism. This key switch is set to
> > either PR_SYS_DISPATCH_ON, PR_SYS_DISPATCH_OFF to enable and disable the
> > redirection without calling the kernel.
> > 
> > The feature is meant to be set per-thread and it is disabled on
> > fork/clone/execv.
> 
> Disabled on exec.  Disabled in the child on clone/fork (and vfork, I
> think).
> 
> That means we don't need to worry about it interacting badly with
> a setuid program, right?

Right, that's the intention.

-- 
Kees Cook