linux-kernel - Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole

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Message-ID: <alpine.LFD.2.00.0902280916470.3111@localhost.localdomain>
Date:	Sat, 28 Feb 2009 09:23:36 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Roland McGrath <roland@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	linux-mips@...ux-mips.org, sparclinux@...r.kernel.org,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole

On Fri, 27 Feb 2009, Roland McGrath wrote:
> 
> I don't know any other arch well enough to be sure that TIF_32BIT isn't the
> wrong test there too.  I'd like to leave that worry to the arch maintainers.

Agreed - it may be that others will want to not use TIF_32BIT too. It 
really does make much more sense to have it as a thread-local status flag 
than as an atomic (and thus expensive to modify) thread-flag, not just on 
x86.

But I think other architectures will find it easier to see what's going on 
if the code is straightforward and they can just fix their 
'is_compat_task()' function. And:

> But here is the patch you asked for.

Yes, this looks much more straightforward. 

And I guess the seccomp interaction means that this is potentially a 
2.6.29 thing. Not that I know whether anybody actually _uses_ seccomp. It 
does seem to be enabled in at least Fedora kernels, but it might not be 
used anywhere.

		Linus
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