linux-kernel - Re: [PATCH] init/do_mounts.c: replace sys_mount() to do

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Message-Id: <201008171541.47078.arnd@arndb.de>
Date:	Tue, 17 Aug 2010 15:41:46 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init/do_mounts.c: replace sys_mount() to do_mount()

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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