Re: lseek() on an iso9660 file

[Rogier Wolff]

H. Peter Anvin wrote:
> Followup to:  <[e-mail]>
> By author:    "Richard B. Johnson" <[e-mail]>
> In newsgroup: linux.dev.kernel
> > 
> > Using Linux 2.4.1 I discovered a problem with lseek on CDROM files
> > (iso9660). I just installed 2.4.17 and found the same problem.
> > 
> > The problem:
> > 
> > (1) A portion of the file, existing on a CDROM,  is read and its the
> >     contents are written to an output file on writable media.
> > 
> > (2) The current input file-position is obtained using
> >     pos = lseek(fd, 0, SEEK_CUR); The value returned is exactly
> >     the expected value.
> > 
> > (3) The rest of the CDROM file is read and written to the output file.
> > 
> > (4) The file-position of the CDROM file is then set back to the saved
> >     position using lseek(fd, pos, SEEK_SET); The value returned is
> >     exactly the expected value.
> > 
> > (5) The CDROM file is then read and its contents are observed to be
> >     scrambled in some strange manner in which word-length groups of
> >     bytes from near the end of the file are interleaved with the
> >     correct bytes. Basically, the file ends up being about twice
> >     as long as the original, with every-other two-byte interval
> >     being filled with bytes from near the end of the file.
> > 
> 
> a) How long is the file?
> b) What is the offset?
> c) What particular iso9660 options (RockRidge, Joliet, zisofs...)
>    does your disk use?
> d) Mount options?
> 
> This seems to be a rather serious bug, so I'd like to get to the
> bottom with it.

My questions would be: "What hardware?".

			Roger. 

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