linux-kernel - Re: + mm-search_binary_handler-mem-limit-fix.patch added to -mm tree

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Date:	Tue, 30 Jan 2007 13:23:49 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Dmitriy Monakhov <dmonakhov@...ru>
Cc:	Andrew Morton <akpm@...l.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, dmonakhov@...nvz.org
Subject: Re: + mm-search_binary_handler-mem-limit-fix.patch added to -mm
	tree

On Tue, 2007-01-30 at 08:40 +0300, Dmitriy Monakhov wrote:
> > > > The function changes mem limit to USER_DS before possible modprobe, but
> > > > never restored it again.
> Truly. The road to hell is paved with good intentions.

:-)

> > For architectures with a split address space there has to be a call
> > set_fs(USER_DS) that switches from KERNEL_DS to USER_DS for the init
> > process. So far this has been done in search_binary_handler and
> > traditionally the kernel starts with KERNEL_DS to make the early
> > copy_from_user calls work.
> > So, what is wrong with always setting USER_DS? We are starting a user
> > space process after all.
> May be add some comment to prevent future attempts to make this place 
> more "correct"?

The use of set_fs(USER_DS) in search_binary_handler is certainly
different compared to the rest. It probably is the only one that is not
paired with a set_fs(KERNEL_DS) or set_fs(old_fs). A comment won't hurt.

-- 
blue skies,
  Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.


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