From: Arnd Bergmann <arnd@arndb.de>
To: Namhyung Kim <namhyung@gmail.com>
Subject: Re: [PATCH] init/do_mounts.c: replace sys_mount() to do_mount()
Date: Tue, 17 Aug 2010 15:41:46 +0200
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Cc: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>, linux-kernel@vger.kernel.org
References: <1282048643-2475-1-git-send-email-namhyung@gmail.com> <201008171515.26175.arnd@arndb.de> <1282051520.1635.7.camel@leonhard>
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On Tuesday 17 August 2010, Namhyung Kim wrote:
> 2010-08-17 (화), 15:15 +0200, Arnd Bergmann:
> > AFAICT there is no need for the copy at all here. The reason that sys_mount
> > copies to a separate page is that it gets passed an arbitrary-length user
> > input.
> 
> Right. But make sure to user options never exceed a page, do_mount() has
> following code:
> 
>         if (data_page)
>                 ((char *)data_page)[PAGE_SIZE - 1] = 0;

Hmm, how very unexpected...

Maybe you can fix that as well in the same patch and move this safeguard
into the copy_mount_options() function? I guess ideally we'd even mark
the arguments to do_mount() as pointers to const, but that might create
an excessive amount of churn.

	Arnd
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