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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080416081523.GB5105@elf.ucw.cz>
Date:	Wed, 16 Apr 2008 10:15:23 +0200
From:	Pavel Machek <pavel@....cz>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
	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 Tue 2008-04-15 22:28:55, Peter Zijlstra wrote:
> On Tue, 2008-04-15 at 22:06 +0200, Pavel Machek wrote:
> 
> > > > I'm not saying this kernel bug is likely to hit in practice. It is
> > > > still a kernel bug.
> > > > 
> > > > Is the slowdown of lseek worth getting rid of this minor bug? Not
> > > > sure, probably yes.
> > > 
> > > I think a slow down is the worse choice.  Adding a note to the
> > > documentation saying that "By the way, on 32bit systems the seek call is
> > > not atomic for 64bit file offsets, so if you happen to issue two at
> > 
> > That would be very wrong addition to documentation. If you really
> > wanted to do something like this, you would probably want to say
> > something like
> > 
> > "Doing concurrent seeks on one file is undefined. Kernel may end up
> > with seeking to some other place."
> > 
> > Unfortunately, you'd have to get this addition into POSIX standard...
> 
> Is not treating the point not similar to undefined? And undefined
> semantics cover pretty much anything, including the current behaviour.
> 
> FWIW I really think this issue is a non-issue; one cannot expect sane
> behaviour of unsynchronized usage of a shared resource.

Why not? Kernel syscalls are traditionally atomic, and Lennard seems
to have found sentence in POSIX that says so.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/