linux-kernel - Re: file offset corruption on 32-bit machines?

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Message-ID: <20080414192928.GM7385@csclub.uwaterloo.ca>
Date:	Mon, 14 Apr 2008 15:29:28 -0400
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	Jan Kara <jack@...e.cz>
Cc:	Bodo Eggert <7eggert@....de>, Diego Calleja <diegocg@...il.com>,
	Jiri Kosina <jkosina@...e.cz>, Michal Hocko <mhocko@...e.cz>,
	Meelis Roos <mroos@...ux.ee>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: file offset corruption on 32-bit machines?

On Mon, Apr 14, 2008 at 09:03:09PM +0200, Jan Kara wrote:
>   Why would it be doing locking? If some nasty user runs the process, he
> *wants* his two threads to race as much as possible and trigger the race.
> And then use corrupted f_pos.

Why would you want to?  You can already set the filepointer explicitly
to any value you want if you have the filehandle.

If you had a file with some security checks for whether the user could
read from it implemented based on locations then you would check it when
you read/write not when you seek, since after all you could just keep
reading until you get to the desired position.

-- 
Len Sorensen
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