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

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Message-ID: <20080415173430.GB4994@elf.ucw.cz>
Date:	Tue, 15 Apr 2008 19:34:30 +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?

Hi!

> > 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.
> 
> Yes bugs are confusing.  An application can't do this on demand so you
> can't write code that relies on the effect between threads.  So it would
> only be a bug, not a bizare feature (that wouldn't even work on 64bit
> machines).

Yes, kernel bugs are confusing ;-).

The "application" could be malware trying to confuse debugger, for
example.

The "application" could be something you are trying to debug.

I did brief reading on lseek man pages, and it does not mention
"kernel may seek to random place if you attempt to seek  from two
threads at the same time". So this is a kernel or manpages bug.

Maybe you can take a look at POSIX if it permits this behaviour? 
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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