Re: file offset corruption on 32-bit machines?

[Jan Kara <jack@suse.cz>]

On Mon 14-04-08 12:22:02, Lennart Sorensen wrote:
> On Mon, Apr 14, 2008 at 06:20:31PM +0200, Jan Kara wrote:
> >   Well, as Jiri Kosina wrote, this isn't a problem unless someone finds
> > a way how to use this race for some attack (and for example making f_pos
> > negative compromises security so it is not so far-fetched as it would
> > seem). So proactively fixing this makes some sence.
> 
> But you would have to be part of that process to affect the filehandle
> wouldn't you?  If you are part of the process already wouldn't it be
> easier to manipulate things directly rather than playing with the
> filehandle position?
  Well, but imagine you have a file /proc/my_secret_file from which you
are able to read from position A:a and B:b but not from position
A:b. Concievably, checks for the file position could be bypassed because of
this race... I know this is kind of dumb example but I can imagine someone
can eventually find something like this. So I guess one spin lock/unlock
pair is a price worth paying in the callpath which is quite long anyway.

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR