linux-kernel - Re: [PATCH] x32: Mask away the x32 syscall bit in the ptrace codepath

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Message-ID: <CALCETrXNi=0WAGMfV5NjeN_xLkG6miEuc6iZBObgofHjUcsFbA@mail.gmail.com>
Date:	Wed, 28 May 2014 14:55:02 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Philipp Kern <pkern@...gle.com>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. J. Lu" <hjl.tools@...il.com>, Eric Paris <eparis@...hat.com>
Subject: Re: [PATCH] x32: Mask away the x32 syscall bit in the ptrace codepath

On Wed, May 28, 2014 at 2:53 PM, Philipp Kern <pkern@...gle.com> wrote:
> On Wed, May 28, 2014 at 11:43 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> However: are you sure that entry_64.S handles this?  It looks like
>> tracesys has higher priority than badsys.  And strace can certainly
>> see out-of-range syscalls. […]
>
> Not only can it see them: It must see that this bit is set as that's
> the only identifier it has to deduce that the binary is running in x32
> mode.
>
> Out of range syscall numbers certainly do not work for auditing right
> now, hence my attempt to patch around it.

There appears to be a completely arbitrary limit of 32*64 syscalls.
There's also an arbitrary limit of 4 arguments.  Both are wrong.  I
have no intention of fixing either.

I'll fix the OOPS, though.

>
> Kind regards and thanks
> Philipp Kern



-- 
Andy Lutomirski
AMA Capital Management, LLC
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