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

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Message-ID: <20080415085740.GA7603@atrey.karlin.mff.cuni.cz>
Date:	Tue, 15 Apr 2008 10:57:41 +0200
From:	Pavel Machek <pavel@....cz>
To:	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
Cc:	Jan Kara <jack@...e.cz>, 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.

Not if you tried to do checking from ptrace monitor.

And heck, yes, it is very confusing to see

seek(somewhere)
write()

ond ptrace and write going somewhere else.
									Pavel
-- 
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