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Message-ID: <20110813151947.GA12495@openwall.com>
Date: Sat, 13 Aug 2011 19:19:47 +0400
From: Solar Designer <solar@...nwall.com>
To: kernel-hardening@...ts.openwall.com
Subject: Re: 32/64 bitness restriction for pid namespace
Vasiliy,
On Sat, Aug 13, 2011 at 07:12:20PM +0400, Vasiliy Kulikov wrote:
> Re: slowdown - my assumptions are:
>
> 1) we don't want any slowdown for legitimate tasks - 64 bit tasks for 64
> bit containers and 32 bit tasks for 32 bit containers.
>
> 2) slowdown of malicious (or broken) tasks is not important.
Right.
> /* work to do in syscall_trace_enter() */
> #define _TIF_WORK_SYSCALL_ENTRY \
> (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \
> _TIF_SECCOMP | _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
>
>
> So, there is a mask, which is used to identify whether a syscall needs
> additional pre/post processing. If divide syscall_trace_enter() into 3
> functions, we'll get what we want. This will result in zero impact on
> the legitimate code (relavite to current behaviour).
>
> One drawback - *tracesys clobbers EAX/RAX, so I still have to patch asm.
I haven't looked into the detail of this, but in general I like the
approach of reusing a check that is already in the code. Please proceed
with this.
Thanks,
Alexander
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